Estimation of the Laminar Flame Speed of Producer Gas from Biomass Gasification Juan J. Hernandez,* Magı ´n Lapuerta, and Clara Serrano Departamento de Meca ´ nica Aplicada e Ingenierı ´a de Proyectos. Universidad de Castilla- La Mancha, Camilo Jose ´ Cela s/n, 13071 Ciudad Real, Spain Andres Melgar Departamento de Ingenierı ´a Energe ´ tica y Fluidomeca ´ nica. Universidad de Valladolid, Paseo del Cauce s/n, 47011, Valladolid, Spain Received January 9, 2005. Revised Manuscript Received May 16, 2005 Because of the importance that the energy use of agricultural and forestry wastes has acquired over the last years, results for the laminar flame speed of producer gas coming from the gasification of lignocellulosic biomass are presented in this work. These results have great interest for the development of combustion models that provide significant information to be used as a tool for the optimization and design of specific internal combustion engines. The CHEMKIN software, together with the GRI-Mech chemical reaction mechanism, has been used to compute the laminar flame speed for different producer gas compositions, different values of pressure and temperature, and different producer gas/air equivalence ratios. The results have been compared with those obtained in an experimental combustion bomb, as well as with the laminar flame speed obtained for conventional fuels, showing that the flame speed of the producer gas is less than that of isooctane but greater than that of methane. A sensitivity analysis shows the influence that the dominant chemical reactions and species have on the laminar flame speed of producer gas at different producer gas/air equivalence ratios. Although good qualitative agreement has been found, some differences between experimental and modeled results at high pressure and temperature are due to the instabilities in the experimental flame. Introduction Lignocellulosic biomass wastes have been used as an energy source for several centuries, with the dominant technology being small furnaces and boilers. In Spain, the use of biomass as a domestic fuel was widespread before the 1960s, until the post-war economic resur- gence allowed the industrial and social development of oil-derived fuels. Since then, biomass was relegated to marginal use. However, recent European and Spanish energy policies 1,2 are strongly encouraging the use of biomass for energy purposes, mainly because of three targets: 3-5 the reduction of CO 2 emissions, the removal of wastes, and the use of indigenous fuels. Usually, forestry and agricultural lignocellulosic wastes are widely distributed. However, these wastes can be used at the same place they are collected to produce power, thus eliminating the cost derived from the storage and transportation to power plants. Because of the low heat value of biomass wastes and the dispersion mentioned previously, gasification constitutes an ef- ficient technology that permits the generation of a low- energy-content gas (producer gas) through a reaction that is deficient in oxygen. This gas is adequate to be used directly in internal combustion engines, such as spark ignition (SI). 6-9 Laminar flame speed is a parameter that embodies the physicochemical properties affecting the combustion and determines the rate of energy released during the process. It also has a significant effect on the perfor- mance and pollutant emissions of internal combustion engines. Although several works have been conducted to calculate the laminar flame speed of H 2 and CO 10-12 (the main fuel species constituting the gas from biomass gasification), some aspects of the thermochemical be- havior of the producer gas have not been systematically * Author to whom correspondence should be addressed. Telephone: 34 926 295300, Ext. 3880. Fax: 34 926295361. E-mail address: JuanJose.Hernandez@uclm.es. (1) Green paper: towards a European strategy for the security of energy supply; Commission of the European Communities, 2002. (2) Plan de Fomento de las Energı ´as Renovables en Espan ˜ a. Instituto para la Diversificacio ´n y Ahorro de la Energı ´a (IDAE), 1999. (3) Palz, W.; Kyramarios, A. In Proceedings of the First World Conference on Biomass for Energy and Industry, 2000; James and James Science Publishers: 2001; Vol. 1, pp pp 6-10. (4) Skutsch, M.; Van Rijn, J. In Proceedings of the 12th European Conference and Technology Exhibition on Biomass for Energy, Industry and Climate Protection, 2002. (5) Strehler, A. Proceedings of the First World Conference on Biomass for Energy and Industry, 2000; James and James Science Publishers: 2001; Vol. 1, pp 191-193. (6) Barisano, D.; De Bari, I.; Nanna, F.; Cardinale, F.; Matera, D.; Cavalere, S.; Viggiano, D.; Fanny, Y. In Proceedings of the First World Conference on Biomass for Energy and Industry, 2000; James and James Science Publishers: 2001; Vol. 1, pp 384-389. (7) Lapuerta, M.; Hernandez, J. J.; Tinaut, F.; Horrillo, A. SAE Technol. Pap. Ser. 2001, 2001-01-3586. (8) Jensen, T. K.; Schramm, J.; Morgen, C. SAE Technol. Pap. Ser. 1999, 1999-01-0571. (9) Sridhar, G.; Paul, P. J.; Mukunda, H. S. Biomass Bioenergy 2001, 21, 61-72. (10) Huang, Y.; Sung, C. J.; Eng, J. A. Combust. Flame 2004, 139, 239-251. (11) McLean, I. C.; Smith, D. B.; Taylor, S. B. In 25th Symposium (International) on Combustion; 1994; p 749. (12) Linteris, G. T. Combust. Flame 1996, 107, 72-84. 2172 Energy & Fuels 2005, 19, 2172-2178 10.1021/ef058002y CCC: $30.25 © 2005 American Chemical Society Published on Web 06/24/2005