Andrés Amell

Performance of a Flameless combustion furnace using biogas and natural gas.

Flameless combustion technology has proved to be flexible regarding the utilization of conventional fuels. This flexibility is associated with the main characteristic of the combustion regime, which is the mixing of the reactants above the autoignition temperature of the fuel. Flameless combustion advantages when using conventional fuels are a proven fact. However, it is necessary to assess thermal equipments performance when utilizing bio-fuels, which usually are obtained from biomass gasification and the excreta of animals in bio-digesters. The effect of using biogas on the performance of an experimental furnace equipped with a self-regenerative Flameless burner is reported in this paper. All the results were compared to the performance of the system fueled with natural gas. Results showed that temperature field and uniformity are similar for both fuels; although biogas temperatures were slightly lower due to the larger amount of inert gases (CO(2)) in its composition that cool down the reactions. Species patterns and pollutant emissions showed similar trends and values for both fuels, and the energy balance for biogas showed a minor reduction of the efficiency of the furnace; this confirms that Flameless combustion is highly flexible to burn conventional and diluted fuels. Important modifications on the burner were not necessary to run the system using biogas. Additionally, in order to highlight the advantages of the Flameless combustion regime, some comparisons of the burner performance working in Flameless mode and working in conventional mode are presented.

Influence of the relative humidity on the air cooling thermal load in gas turbine power plant

Abstract The gas powered thermal share of the generation of electricity in Colombia has increased in a significant way in the last decade, to the extent that approximately 2800 MW have been installed throughout using gas turbines. Gas turbines have the drawback of decreasing the power output when the ambient temperature increases. To alleviate this effect the air is cooled before entering the machine using a variety of technologies. This work examines the influence of the relative humidity on the atmospheric air-cooling thermal load, for the sites where gas powered thermal station have been installed in Colombia. Results of this work show that due to high relative humidities the cooling thermal load is 1.5–1.9 times higher compared to regions in other countries that show average relative humidities of 30%. Without question, this implies higher costs in Colombia when implementing two types of cooling technique, namely: vapor compression cycle and ice storage.

Numerical Simulation of a Flameless Combustion Furnace with Mixtures of Methane and a Sub-Bituminous Pulverized Coal

ABSTRACT A numerical study of flameless combustion with mixtures of methane and a sub-bituminous pulverized coal was carried out. The analyzed mixtures were 0%, 25%, 50%, 75%, and 100% pulverized coal (energy based). The numerical study was performed using the geometry of a laboratory-scale furnace, which was originally designed to obtain the flameless combustion regime burning natural gas. The turbulence was modeled by means of the standard k- model; the interaction between combustion and turbulence was modeled with the eddy dissipation model using a global reaction mechanism for methane. Also, the pulverized coal was modeled as a discrete phase using the Lagrangian approach, where oxidation and gasification reactions were taken into account to model coal consumption. Additionally, all simulations were done keeping the thermal power constant at 28 kWth and the excess air coefficient was fixed at 1.2. It was found that there are no significant changes in the temperature field uniformity when methane is replaced by pulverized coal, and the size of the reaction zone stays quite similar to the case of burning pure methane. Furthermore, for some cases an improvement of the recirculation factor was obtained. Based on the numerical results, it was concluded that it would be possible to obtain a stable flameless combustion regime for the analyzed methane/pulverized coal mixtures.

COMPARACIÓN DEL MUESTREO DE ESPECIES QUÍMICAS EN ZONAS REACTIVAS MEDIANTE EL USO DE SONDA CON Y SIN CUELLO SÓNICO

El analisis de los productos de combustion en las zonas de reaccion y al interior de camaras de combustion requiere, con respecto a las medidas efectuadas en chimeneas, de equipos y de metodos particulares de muestreo. Asi por ejemplo, en las zonas donde hay presencia de llama se deben utilizar dispositivos experimentales no intrusivos, tales como las tecnicas laser, o intrusivos como las sondas de muestreo. El empleo de los primeros implica altos costos mientras que el de los segundos deben garantizar que las reacciones de combustion no continuen al interior de la sonda pues de lo contrario se producen errores importantes en la medicion. En este trabajo se presenta una comparacion de los resultados obtenidos al realizar muestreos al interior de la zona de reaccion de una llama de premezcla parcial empleando dos tipos de sondas: una con cuello sonico y enfriamiento convectivo de la muestra y la otra constituida simplemente por un tubo en acero inoxidable; para identificar si existen efectos termicos y cinetico - quimicos que generen diferencias en la medicion de las especies mayoritarias. Los resultados muestran que al emplear una sonda con un tubo liso se estarian presentando errores en las mediciones de CO2 y CO cercanos al 7,0% y en las de O2 superiores al 14%. The analysis of combustion products inside flames reaction zones and combustion chambers requires special equipment and methods of sampling compared to measurements made in chimneys. For example, non-intrusive experimental devices, such as laser techniques, or intrusive ones, such as sampling probes, should be used in zones where a flame is present. The use of the first ones means high costs, while the second ones must guarantee that the combustion reactions do not continue inside the sample probe; otherwise significant errors occur in the species measurements. To identify whether there are thermal and chemical kinetic effects that produce differences in the major species measurement, this paper presents a comparison of sampling results inside the reaction zone of a partially premixed flame when two types of sample probes are used: one with a sonic neck and a convective cooling of the sample, and another made just of a straight stainless steel tube. The results show that when using a straight tube there are errors in CO2 and CO measurements up to 7.0%, and errors in O2 measurements above 14%.

Metodología para el Desarrollo de Sistemas de Combustión Sin Llama

A methodology to design flameless combustion heating equipment is presented. The design of flameless combustion devices requires an appropriate methodology to guarantee the necessary conditions to obtain this combustion mode. Nevertheless, such methodologies are not available in the scientific literature. For this, a combination of dynamic scaling, based on air/gas impulse ratio, and numerical simulation with FLUENT® has been employed to get suitable geometric configurations and dimensions for discharging fuel and comburent air. The proposed methodology has been applied to the design of a 20 kW experimental furnace using natural gas as fuel. The validity of the methodology has been verified with stable flameless combustion operation in the furnace.