Considering the potential of using concentrating solar power systems to supply the heat required for the allothermal gasification process, this study analyzes hydrogen production in such a system by assuming typical radiative heat flux profiles for a receiver of a central tower concentrated solar power (CSP) plant. A detailed model for allothermal gasification in a downdraft fixed bed tubular reactor is proposed. This considers solid and gas phases traveling in parallel flow along the reactor. Results for temperature and gas profile show a reasonable quantitative agreement with experimental works carried out under similar conditions. Aiming to maximize H2 yield, eight Gaussian flux distributions, similar to those typical of CSP systems, each with a total power of 8 kW (average heat flux 20 kW/m2), but with varying peak locations, were analyzed. The results show a maximum producer gas yield and a chemical efficiency of 134.1 kmol/h and 45.9% respectively, with a molar concentration of 47.2% CO, 46.9% H2, 3.3% CH4, and 2.6% CO2 for a distribution peak at z = 1.4 m, thus relatively close to the flue gas outlet. Hydrogen production and gas yield using this configuration were 4% and 2.9% higher than the achieved using the same power but homogeneously distributed. Solar to chemical efficiencies ranged from 38.9% to 45.9%, with a minimum when distribution peak was at the reactor center. These results are due to high temperatures during the latter stage of the process favoring char gasification reactions.

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How to cite: Duarte, J., et al., Thermodynamic Analysis of SelfIgnition in Spark-Ignited Engines Operated with Alternative Gaseous Fuels, TECCIENCIA, Vol. 11 No. 20,[57][58][59][60][61][62][63][64][65] AbstractCurrently, detailed studies exist on the self-ignition phenomenon in liquid fuels and even for natural gas. However, studies for syngas are quite limited and existing ones are mainly focused on combustion kinetics and do not study self-ignition prior to the ignition point. This paper presents the development of a thermodynamic analysis to study the self-ignition phenomenon in gaseous alternative fuels during the compression stroke in spark-ignited internal combustion engines. Analysis takes into account the fuel composition, relevant process parameters, and variation due to pressure and temperature intake changes. The approach is focused on equilibrium thermodynamics, which easily allows estimating engine operating conditions. These results permit studying adequate compression ratios to obtain good efficiencies, as those achieved by using natural gas, but in heat engine applications to generate power with low-methane-number syngas fuels. Keywords: Self-ignition, Gaseous Fuels, Combustion, Internal Combustion Engines ResumenEn la actualidad, existen estudios detallados del fenómeno de la auto-detonación en combustibles líquidos e inclusive para el gas natural. Sin embargo, los estudios para gas de síntesis son muy limitados y los existentes se centran principalmente en la cinética de la combustión y no se ha estudiado el autoencendido antes del punto de ignición. En este trabajo se presenta el desarrollo de un análisis termodinámico para estudiar el fenómeno de auto-ignición en combustibles gaseosos alternativos durante la carrera de compresión, cuando son utilizados en motores de encendido provocado. El análisis tiene en cuenta la composición del combustible, los parámetros relevantes del proceso y la influencia debido a los cambios de presión y temperatura en la admisión. El enfoque se centra de la termodinámica de equilibrio, lo que permite una estimación práctica de la condición de funcionamiento del motor. Estos resultados permiten estudiar las relaciones de compresión adecuadas con el fin de obtener eficiencias similares a las obtenidas utilizando gas natural, pero en aplicaciones de motores térmicos para la generación de energía eléctrica utilizando gas de síntesis de metano bajo número como combustible