Se presentan los resultados de un estudio sobre la significancia y la optimización de algunas variables (granulometría, velocidad de aire, contenido de biomasa y disposición del reactor) en el poder calorífico del gas de síntesis obtenido de la gasificación de biomasa (carbón vegetal y cuesco de palma africana). Mediante un diseño de experimento se evaluaron las cuatro variables que oscilaban entre 8-13mm para la granulometría, 0.8-1.4m/s para la velocidad del aire, 0-100 para el contenido de biomasa y ascendentedescendente para la disposición del reactor. Se encontró que los factores correspondientes a la granulometría y el contenido de biomasa resultan ser los más significativos en el poder calorífico del gas. Un poder calorífico máximo de 3.84MJ/Nm 3 se obtuvo con la disposición descendente del reactor, alimentación de carbón vegetal con granulometría de 13mm y suministro máximo de flujo de aire. La verificación del punto óptimo de operación mostró que tales condiciones de operación favorecían la producción de un gas con un alto poder calorífico.

This paper presents a comparison between the behavior predicted by a computational fluid-dynamic model (CFD) and an analytical model for a commercial vortex tube using air and methane as working fluids, in addition to a three-dimensional mesh for this purpose. The numerical simulation of the turbulent, compressible and high vorticity flow was carried out using RANS equations, the Realizable k-e turbulence model and STAR-CCM+ as software for the equations solution. The variables measured in this work were temperature, pressure and velocity at the exit nozzles of the vortex generator and the tube discharges, resulting in errors of less than 16% between CFD and the analytical model. This numerical study represents a first approximation of the vorticityphenomenon and has been developed in order to establish a prototype simulation model that provides, under certain inlet conditions to the process, preliminary information on the vortex tube industrial implementation for obtaining liquefied natural gas.

ResumenEn esta investigación se llevó a cabo la comparación entre diferentes soluciones numéricas para un modelo matemático de combustión teórica y la variación de la conductividad del cuesco de palma en un reactor de lecho fijo descendente mediante combinaciones entre los esquemas compactos (EC) de diferencias finitas (DF) de orden 2, 4 y 6 y los métodos de integración de Runge Kutta (RK) para n=1, 2 y 4. Los resultados obtenidos mostraron que la aproximación obtenida bajo el EC y el método de integración RK, ambos de orden 4, fué la más cercana al punto de referencia analizado (EC de orden h 6 , sistema integrador RK de orden 4, malla de 80x80 y paso de tiempo de 1 segundo) con diferencias del orden de 13.6E-05 % y errores porcentuales más significativos entre 7.22% y 8.1% a una altura aproximada de 0.5m medida desde el fondo de la tolva. Además, se muestra la correlación entre las variables posición-temperatura y temperatura-conductividad para 21 puntos escogidos x-espaciados distribuidos sobre una línea que va desde 0≤y≤H. Se corrobora que la conductividad del material aumenta a medida que se incrementa la temperatura y es inversamente proporcional a la distancia medida desde la base menor de la tolva. Palabras clave: esquemas compactos; diferencias finitas; métodos de integración; biomasa; conductividad térmica Comparison of Numerical Solutions for a Mathematical Model of Theoretical Combustion and Conductivity Variation of Shell Palm in an Fixed Bed Reactor AbstractIn this investigation numerical solutions for a mathematical model of theoretical combustion and conductivity variation of the shell palm in an downdraft fixed bed reactor were compared by means of combinations between order 2, 4 and 6 of finite difference (FD) compact schemes (CE) and Runge Kutta (RK) integration methods (n = 1, 2 and 4). The results obtained showed that the approximation obtained under 4 order CE and the integration method RK(n=4), was the closest with 13.6E-5% to the reference point (order 6 of CE, integrating system RK of order 4, mesh 80x80 and 1 second step time) and between 7.22% and 8.1% significant errors at an approximate height of 0.5m measured from the bottom hopper. In addition, the correlation between the position-temperature and temperature-conductivity variables for 21 x-spaced points distributed over a line from 0≤y≤H is presented. This corroborates the fact that the conductivity of the material increases as the temperature increases and is inversely proportional to the distance measured from the bottom hopper.

A chemical equilibrium model for fixed-bed gasification is developed, which allows the prediction of the syngas composition, the amount of residual coal or ash, as well as the amount of tars as a function of the gasification temperature and the elemental composition of the biomass and the tars. Moreover, the combustion heat of the gas fuel is calculated, as well as the conversion and process efficiency, in order to perform further analyses which allow the determination of energy potential for different types of biomass under several conditions of moisture and equivalence ratio of gasifying agent. Performance of the proposed model is compared to prediction of some models which were found to be relevant in the literature review. An assessment to the model is also carried out. For this purpose, a case-study is performed for African palm (Elaeis guineensis) shells using a commercial gasifier. Experimental data obtained from the biomass used in the case-study are used to feed the model and perform the assessment. Actual results and model predictions (results) are compared varying the equivalent relation between 0.05 and 0.65, and the moisture content form biomass between 0 and 20%. This case is proposed as a benchmark case for further applications.

This paper studied, through an experiment design, the significance of particle size, air speed and reactor arrangement for palm shell micro-gasification process in order to optimize the heating value of the syngas obtained. The range of variables was 8 to 13 mm for particle size, 0.8-1.4m/s for air velocity, and updraft or downdraft for the reactor type. It was found that the particle size and air velocity factors were the most significant in the optimization of the output variable, syngas heating value. A heating value of 2.69MJ / Nm3 was obtained using a fixed bed downdraft reactor, with a particle size of 13 mm and 1.4 m/s for air speed; verification of the optimum point of operation under these conditions verified that these operating conditions favor the production of a gas with a high energy value.