Gasification: biomass

Resources such as biomass could provide a clean and sustainable resource for hydrogen production. As with fossil fuels, the processes that produce hydrogen gas from biomass all create carbon dioxide, but because the biomass acts as a carbon sink during the growing phase, the net carbon emission of the whole cycle is neutral. 

2 gasifier is also based on an indirectly heated gasification process. The heat needed for the gasification stage is introduced into the process by a heat carrier (e.g., spheres of corundum). One possible process layout for hydrogen production based on the staged-reforming process is shown in Fig. 10.4. 

7 A review of various biomass gasification processes can be found in BMELV, 2005 Boukis et al., 2005 Ni et al., 2006  

The gasification process can use a variety of biomass resources, such as agricultural residues and wastes, or specifically grown energy crops. The technologies for gasifying 

Facilities using renewable biomass to generate electricity currently produce enough power for about 7 million American households per year.30 Many more biomass generation plants are not on the public power grid, but produce electricity and heat energy for manufacturing operations, primarily in the forest products industry. 

The majority of these operations use boiler technology, which involves the direct combustion of biomass materials 

30 Source httpyAvww.eere.energy.gov/biopower/bpliMibrary/li gasification.htm. 

Biomass gasifiers have the potential to be up to twice as efficient as using conventional boilers to generate electricity. For even greater efficiency, heat from the gas turbine exhaust can be used to generate additional electricity with a steam cycle. These improvements in efficiency can make environmentally clean biomass energy available at costs more competitive with fossil fuels. 

Grate-fired combustors are in use for old biomass-fired plant, while fluid bed combustors are rapidly becoming the preferred technology for biomass combustion because of their low NOx emissions. 

Gasification is the conversion by partial oxidation at elevated temperature of a carbonaceous feedstock into a gaseous energy carrier consisting of permanent, noncondensable gases. Ideally, the process produces only a non-condensable gas and an ash residue. However, since gasification processes are carried out far from equilibrium, tars (condensable organic material) are produced and the ash resi- 

Gasifiers have been designed in various configurations [4, 5, 24], each having its own advantages and disadvantages, in terms of product gas composition and operating parameters. 

Fixed bed gasifiers are generally used for small-scale operation with gas engines, having an electrical output of about 80-500 kWe. They divide into updraft and downdraft gasifiers. 

Fluidized beds provide many features not available in the fixed-bed types, including high rates of heat and mass transfer and good mixing of the solid phase, which means that reaction rates are high and the temperature is more or less 

The major challenge for the utilization of biomass as renewable energy source in combined gasification/gas turbine plants is the efficient removal of tar and particulates from the feed gas of the gas turbine [11]. This is a another promising application of the concept of catalytic filtration, but the technical development is still in the laboratory state. 

Nickel-based steam reforming catalysts are very efficient for the decomposition of tars and ammonia in biomass gasification gas. Ceramic candle filters can be applied to remove particles at high temperature. It is proposed to use nickel-activated alumina candle filters for the simultaneous removal of tar, ammonia and particles from biomass gasification gas [12]. 

Engelen et al. prepared a novel catalytic nickel-calcium-coated alumina candle filter for the combined removal of tar and particulates from hot biomass gasification gas [13]. Special attention was paid to the improvement of the catalyst s resistance against H2S poisoning. Deactivation tests were performed with benzene and naphthalene as tar model compounds in a simulated dust-free gasification gas. The filter did not change the H2S content in the gas. Naphthalene showed a higher conversion (96-98 % at 100 ppm H2S) than the less problematic benzene. Both compounds 

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Whilst the basic process for generation and conversion of syngas is well established, production from biomass poses several challenges. These centre on the co-production of tars and hydrocarbons during the biomass gasification process, which is typically carried out at 800 °C. Recent advances in the production of more robust catalysts and catalytic membrane reactors should overcome many of these challenges. 

Surface Analyses of Cobalt Catalysts for the Steam Reforming of Tar derived from Biomass Gasification... 

Keywords cobalt catalyst, naphthalene, steam reforming, biomass, gasification, tar 1. Introduction... 

Biomass gasification offers the potential for producing a fuel gas that can be used for power generation system or synthesis gas applications. The volatile matter contains a considerable amount of tar which is a complex mixture of aromatics. Despite extensive research efforts tar formation which causes the pipe plugging and the reduction of conversion efficiency is still a major problem in biomass gasification systems [1-6]. 

Process flow schematic for the production of fuels, including hydrogen, based on biomass gasification. (Reproduced from Hamelinck, C., and Faaij, A.P.C. /. Power Sources, 111(1), 1-22,2002. With permission.)... 

The FICFB process concept applied in the 8 MWlh Cussing plant (Austria). (Reproduced from Knoef, H., Handbook Biomass Gasification. BTG (Biomass Technology Group), Enschede, 2005. With permission.)... 

The heatpipe reformer process concept for hydrogen-rich syngas production. (Reproduced from Karellas, S., Metz, T., Kuhn, S., and Karl, J., Online analysis of the tar content of the product gas from biomass gasification. Application on the BIOHPR. 14th European Biomass Conference Exhibition, Biomass for Energy, Industry and Climate Protection, ETA-Renewable Energies, Paris, 2005. With permission.)... 

Source Reproduced from Knoef, Hv Handbook Biomass Gasification. BTG (biomass technology group), Enschede, 2005. With permission. 

DOE, Hydrogen, Fuel Cells and Infrastructure Technologies Program, Multi-year Research, Development and Demonstration Plan. 2003 available at http //wwwl.eere.energy.gov/hydrogenandfuelcells/ production/biomass gasification.html (accessed March 2008). 

Boerrigter, H. Rauch, R., Review of Applications of Gases from Biomass Gasification. ECN-RX— 06-066, ECN, Petten, 2006. 

Prins, M. J., Thermodynamic Analysis of Biomass Gasification and Torrefaction. PhD Thesis, Technical University of Eindhoven, Eindhoven, 2005. 

Paisley, M. A. Welch, M. J., Biomass gasification combined cycle opportunities using the future energy Silvagas gasifier coupled to Alstom s industrial gas turbines. ASME Turbo Expo 2003, ASME, Paper GT2003-38294, Atlanta, GA, 2003. 

Caballero, M. A. Aznar, M. P. Gil, J. Martin, J. A. Frances, E. Corella, J., Commercial steam reforming catalysts to improve biomass gasification with steam-oxygen mixtures. 1. Hot gas upgrading by the catalytic reactor. Industrial and Engineering Chemistry Research 1997,36(12), 5227-5239. 

Aznar, M. P. Caballero, M. A. Corella, J. Molina, G. Toledo, J. M., Hydrogen production by biomass gasification with steam-02 mixtures followed by a catalytic steam reformer and a CO-Shift system. Energy and Fuels 2006, 20, 1305-1309. 

Matsumura, Y. Minowa, T., Fundamental design of a continuous biomass gasification process using a supercritical water fluidized bed. Journal of Hydrogen Energy 2004, 29, 701. 

Boukis, N. Galla, U. Diem, V. Dinjus, E., Biomass gasification in supercritical water First results of the pilot plant, In Science in Thermal and Chemical Biomass Conversion, Bridgwater, A. V. Boocock, D. G. B., Eds., CPL Press, Victoria, 2004, pp. 975-990. 

In early 1900s, biomass gasification processes were also widely used to manufacture synthetic gases for production of fuels, chemicals, and hydrogen. During World War II, over 1 million air-blown gasifiers were built to produce synthetic gas from wood and charcoal to power vehicles and to generate steam and electricity.3... 

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