• Energy Research

El aumento en la demanda energética y las emisiones contaminantes, así como la dependencia de los combustibles fósiles a nivel mundial, genera la necesidad de buscar estrategias enfocadas en una mayor eficiencia y mejoramiento en los procesos de transformación energética. En este estudio se evaluó numéricamente el proceso de cocción de ladrillos al interior de un horno tipo Hoffman, utilizando un enfoque de dinámica de fluidos computacionales (CFD), analizando los campos de temperatura y los patrones fluidodinámicos al interior del proceso. Los resultados obtenidos además de analizar en detalle cómo se dan los fenómenos térmicos al interior del horno evidenciaron varios campos de estudio en los que se debe profundizar para lograr una mejora energética en la cocción de ladrillos y por tanto mayor eficiencia.

El aumento de la demanda energética, así como de las emisiones contaminantes ha generado un incremento de la investigación de tecnologías que permitan mitigar ambas problemáticas a nivel mundial. Dentro de las alternativas para mejorar la eficiencia de los procesos térmicos, el régimen de combustión sin llama se presenta como una de las alternativas más promisorias, puesto que permite obtener altos valores del rendimiento térmico mediante el mejoramiento de la transferencia de calor y del proceso de combustión, con la consiguiente reducción de las emisiones contaminantes. Debido a esto, en el presente estudio se realiza una revisión del estado del arte de dicha tecnología, haciendo énfasis en los aspectos fenomenológicos asociados, las principales características del régimen y su estabilidad, pasando por los mecanismos de obtención y la presentación de una serie de estudios, tanto a nivel nacional como internacional, en los que se utilizaron combustibles fósiles y alternativos. La revisión finaliza con la discusión de algunos casos en los cuales se ha implementado el régimen a nivel industrial.

Abstract Several studies on the laminar burning velocity of syngas mixtures have been conducted by various researchers. However, in most of these studies, dry air was used as the oxidizer, whereas very few studies have been conducted on syngas combustion in oxygen – enriched air. In this work, a numerical and experimental study on the laminar burning velocity of a mixture of H 2 , CO and N 2 (20:20:60 vol%) was performed using air enriched with oxygen as the oxidizer, varying the oxygen content from 21% up to 35% for different equivalence ratios. Numerical calculations were conducted using three detailed reaction mechanisms and transport properties. Flames were generated using contoured slot-type nozzle burners, and Schlieren images were used to determine the laminar burning velocity with the angle method. The experiments were performed under the conditions of Medellin (1550 m.a.s.l.), 0.838 atm and 298 K. The laminar burning velocity increases with the concentration of the oxygen in the mixture due to the increase of the reaction rate; for a stoichiometric mixture, the laminar burning velocity increases by almost 25% with an increment of 4% of oxygen in the oxidant. However, the flammability limits also increase, allowing stable flames to exist in a wider range of equivalence ratios.

Abstract The laminar burning velocity of syngas mixtures has been studied by various researches. However, most of these studies have been conducted in atmospheric conditions at sea level. In the present study, the effect of sub atmospheric pressure was evaluated on the laminar burning velocity for a mixture of H 2 , CO and N 2 (20:20:60 vol%) in real sub atmospheric condition. The measurements was conducted in an altitude of 2130 m.a.s.l (0.766 atm) and 21 m.a.s.l (0.994 atm) to evaluate the effect of pressure, the temperature and relative humidity were controlled using an air conditioning unit and was maintained in 295 ± 1 K and 62.6 ± 2.7% respectively. The Flames were generated using contoured slot-type nozzle burner, and an ICCD camera was used to capture chemiluminescence emitted by OH∗-CH∗ radicals present in the flame and thus obtain the flame front and determinate the laminar burning velocity using the angle method. The experimental results were compared with numerical calculations, conducted using the detailed mechanisms of Li et al. and the GRI-Mech 3.0. It was found that the laminar burning velocity increases at lower pressure, for an equivalence ratio of 1.1, the laminar burning velocity increases by almost 23% respect to the sea level conditions.

ABSTRACT: The present work numerically and experimentally studies the mixture of 30% syngas and 70% natural gas (SG-NG), by volume, and compares performance to pure natural gas (NG). The experimental measurements were carried out in a semi-industrial regenerative furnace originally designed for pure natural gas. A 25 kW thermal input and a 1.2 excess air ratio were maintained throughout. Temperatures and species were measured inside the combustion chamber. The effect of the syngas on the reaction zone location was determined by imaging spontaneous chemiluminescence. The effect of preheating was also studied for the SG-NG mixture. CFD modeling was used to analyze the effects on recirculation patterns. SG-NG exhibited an average temperature decrease of 6% compared to NG, due to the greater recirculation and increased CO2 in the flue gases. The species uniformity remained consistent, while the thermal uniformity factor (RTU) decreased by 10.5%, indicating greater uniformity. NOx emissions decreased by almost 50% for the SG-NG mixture. The addition of syngas improved the reactivity and displaced the reaction zone upstream. Without preheating, the recirculation and the reactant dilution decrease, generating a disturbance in the thermal uniformity (RTU increase by 65%) and the reaction zone was displaced downstream. COL0002466