31-01-2013, 10:22 AM
Bio‐SNG – Demonstration of the production and utilization of synthetic natural gas (SNG) from solid biofuels Specific Targeted Research or Innovation Project
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Background
The utilisation of natural gas is of high importance within the European energy system. Intensive activities concerning the substitution of natural gas with so called synthetic natural gas respectively biomethane are currently ongoing based on the objectives in the contexts of climate protection and diversification of supply sources. Therefore, a number of concepts are available. Here, the production of biomethane via thermo‐chemical conversion of solid biofuels ‐ so called Bio‐SNG ‐ is a favourable addition to the provision of biomethane from bio‐chemical conversion routes (biogas). Technologies for the feed‐in, the distribution as well as the utilisation of biomethane are market‐ready and applied commercially.
The biogas production technology based on anaerobic digestion, wet fermentation of biomass residues (and wastes) as well as from energy crops (e.g. maize silage) is mature. The conversion of biomass into Bio‐SNG is not that far developed yet. Currently, biomass gasification based on steam for the production of heat and electricity is successfully demonstrated and market‐ready. The European project “Demonstration of the production and utilisation of synthetic natural gas” has started in May 2006 against the background of the required subsequent methanation that was implemented in a pilot stage with a few kW thermal capacity.
Objectives
The objective of the “Bio‐SNG”‐project was to demonstrate the SNG production from woody biomass in the 1 MW‐range using steam gasification, advanced gas cleaning, methanation and gas upgrading as a part of an innovative 8 MW biomass CHP gasification plant and to integrate this Bio‐SNG into the existing energy infrastructure (i.e. fuel station for vehicles). To meet the specifications required for the gas utilisation in vehicles or the gas‐feeding into an existing natural gas grid, the produced SNG has to be upgraded. With this upgraded renewable gaseous fuel, cars were refuelled. These cars are currently in operation for the purpose of demonstrating the application of Bio‐SNG within the transportation sector.
Basics characteristics of Bio‐SNG
The SNG production is characterised by the possibility that relatively small conversion units with capacities in a range of 10 up to 100 MWbf can be used. Hence, the conversion of locally available lignocellulosic biomass into biomethane is possible. The production of synthetic biofuel, electricity and heat (so called tri‐generation) allows for high overall efficiencies (e.g. high CO2 mitigation potential) within the entire production process. In comparison to the production of BtL fuels (like Fischer‐Tropsch‐fuels), the SNG production system is marked by lower technical and financial risks because of a lower complexity of technology that (e.g. synthesis and fuel treatment). It also works with smaller units. Based on these circumstances, a rapid and easy market entrance is possible. Methane and in this context Bio‐SNG has a high market potential and is well known as an energy carrier (transport sector, stationary applications, heat and power) as well as for material utilisation. Within the existing and well developed natural gas grid in Europe, SNG can easily be fed‐in and distributed to the final consumer in industry and households. Beside the above mentioned advantages, the combustion properties of methane are already well known and characterised by comparably low emissions.
State of the art
The production of SNG can occur within a very promising concept via the steam gasification of woody biomass, gas cleaning, subsequent methanation and a raw SNG up‐grading. The steam gasification and the gas cleaning have been demonstrated successfully in a full technical scale (8 MW thermal capacity) at the biomass combined heat and power (CHP) gasification plant in Güssing/Austria. Here, during the last years numerous experiences in the commercial operation were generated. Steam gasification leads to producer gas with a relatively high content of hydrogen and methane as well as a low content of nitrogen. These properties are necessary for an efficient SNG production.
Consortium
The activities in the Bio‐SNG project were conducted by a consortium consisting of institutions from Austria, Czech Republic, France, Germany and Switzerland, and the coordination of the entire project was carried out by the German BiomassResearchCentre (DBFZ). The project partners from research and industry are shown in Figure 1.
Detailed Engineering
The detailed engineering was split into various activities in order to comply with the nature of such a research and development project in the field of process engineering. This involved some specialities such as communication with the research partners for finding the right basis for the detailed engineering or to create the flexibility required to accommodate the development work, which could not exactly be defined early in the project as it would be required for conventional detail engineering. Furthermore, some input from the ongoing R&D work was integrated into the design during the course of the project such as the results of the work associated with the catalyst testing.
Conceptual design
The engineering started with the review of the available process concept. The conceptual design of the plant was developed being based on the R&D needs, the expected operation requirements of the methanation catalyst and the product specifications of pipeline‐grade SNG. The different process options were calculated and the most suitable ones were selected. Various parameters had to be fixed such as pressures, temperatures, efficiencies or materials. A special emphasis was all the time that the catalyst shall ‘feel well’ and that decision taken would allow later for scale up to industrial plant size.