EVALUACIÓN DEL DESEMPEÑO DE UN LECHO FLUIDIZADO DE TIPO SURTIDOR (LFTS) PROVISTO DE GUIADORES CILINDRICOS NO POROSOS EN LA DESAPONIFICACIÓN DE GRANOS DE QUINUA
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Inv. y Des.
Abstract
Este trabajo de investigación evalúa el uso de guiadores en un lecho fluidizado de tipo surtidor (LFTS) en el proceso de remoción de saponinas de quinua real (ecotipo amarilla). Se utilizaron guiadores cilíndricos no porosos con superficies abiertas laterales de 30 mm y 50 mm de altura medida desde la parte inferior. Se utilizó 2 reactores de vidrio cilíndrico cónico de 7,44 y 14,34 cm de diámetro y conos de 30° y 45° respectivamente, con boquillas que varían de 1,5 a 5 mm de diámetro de orificio, conectadas a un flujómetro digital alimentado de aire por un compresor de 400 lmin-1de capacidad. En pruebas de caracterización del lecho con y sin guiadores se evaluó las relaciones entre la velocidad lineal de aire en la entrada al surtidor, la presión manométrica, el flujo volumétrico de aire, tiempo de ciclo de la partícula y la velocidad másica de circulación de sólidos dentro del LFTS. Posteriormente, se elaboró un diseño experimental factorial de 4 factores a 2 niveles (2(4)) por duplicado, generando 32 corridas en las que se evaluó el efecto del diámetro de lecho, el diámetro de boquilla, la altura de lecho y la altura de la zona de entrada de granos al guiador en la pérdida de masa, concentración residual de saponinas en el grano y el consumo específico de energía. La mayor eficacia de remoción de saponinas corresponde a las condiciones de operación del LFTS con menor diámetro de boquilla (Øb = 2 mm), mayor altura de zona de entrada de granos (H D = 50 mm), mayor diámetro de lecho (14,4 cm) y menor altura de lecho (H L=21,5 cm). En estas condiciones geométricas, a los 81 minutos de procesamiento, se logró una concentración residual de saponinas del 0,032 % y una eficiencia de remoción de saponinas del 52,64 %. A mayores velocidades lineales en la entrada al surtidor y mayores frecuencias de ciclo del grano se obtiene mejores eficiencias de remoción de saponinas y menores concentraciones residuales de saponinas en el grano. En general, se puede concluir que para obtener concentraciones residuales mínimas de saponinas en los granos y eficiencias de remoción superiores al 90%, será apropiada cualquier configuración que genere velocidades lineales en la entrada al surtidor entre 1 000 y 1 300 ms-1 y frecuencias del orden de 20 CPM. Menores velocidades de circulación de granos en un LFTS con guiador, respecto de las que se obtienen en lechos sin guiador, generan una falta de uniformidad en la concentración de saponinas en el grano tratado y menores eficiencias de remoción.
This research work evaluates the use of draft-tubes in spouted beds applied to the process of saponins removal from bitter quinoa grains (yellow ecotype). Non-porous cylindrical draft tubes were used with lateral open surfaces of 30 and 50 mm in height measured from the bottom. The experimental runs used two conical cylindrical glass vessels of 7.44 and 14.34 cm diameter and cones of 30° and 45° respectively, provided with nozzles varying between 1.5 and 5 mm, connected to a digital flowmeter supplied with air by a compressor of 400 Lmin-1 capacity. In tests of characterization of the bed with and without draft-tubes, experimental relationships among the linear velocity of air at the inlet of the spout, the gauge pressure, the volumetric flow of air, the particle's cycle time and the mass velocity of the circulation of solids were evaluated. Subsequently, a two-level factorial experimental design (2(4)) was applied for the following factors: diameter of bed, diameter of gas inlet nozzle, height of bed and height of entrainment zone. As dependent variables, the loss of mass, concentration of saponins in the grain and specific energy consumption were evaluated. The highest saponin removal efficiencies correspond to the following geometrical conditions of the spouted bed with draft-tube: smaller nozzle diameter (Øb = 2 mm), major distance of entrainment zone (H D = 50 mm), major diameter of bed (ØL = 14,4 cm) and lower height of bed (H L = 21, 5 cm). Under these geometric conditions, after 81 minutes of processing, the draft-tube LFTS achieved a concentration of saponins (0.0325%) and a saponins removal efficiency of 52.64%. At higher linear air inlet velocities and higher grain cycle frequencies, better efficiencies of saponin removal and lower residual concentrations of saponins in the grain are obtained. In general, it can be concluded that to obtain minimum residual concentrations of saponins in the grains and removal efficiencies greater than 90%, any configuration that generates linear air inlet velocities of 1 000 to 1 300 ms-1 and frequencies of 20 CPM will be appropriate. Lower grain circulation mass flows in draft-tube spouted beds, compared to those obtained in conventional spouted beds, generate a lack of uniformity in the removal of saponins in the treated grains and lower efficiencies.
This research work evaluates the use of draft-tubes in spouted beds applied to the process of saponins removal from bitter quinoa grains (yellow ecotype). Non-porous cylindrical draft tubes were used with lateral open surfaces of 30 and 50 mm in height measured from the bottom. The experimental runs used two conical cylindrical glass vessels of 7.44 and 14.34 cm diameter and cones of 30° and 45° respectively, provided with nozzles varying between 1.5 and 5 mm, connected to a digital flowmeter supplied with air by a compressor of 400 Lmin-1 capacity. In tests of characterization of the bed with and without draft-tubes, experimental relationships among the linear velocity of air at the inlet of the spout, the gauge pressure, the volumetric flow of air, the particle's cycle time and the mass velocity of the circulation of solids were evaluated. Subsequently, a two-level factorial experimental design (2(4)) was applied for the following factors: diameter of bed, diameter of gas inlet nozzle, height of bed and height of entrainment zone. As dependent variables, the loss of mass, concentration of saponins in the grain and specific energy consumption were evaluated. The highest saponin removal efficiencies correspond to the following geometrical conditions of the spouted bed with draft-tube: smaller nozzle diameter (Øb = 2 mm), major distance of entrainment zone (H D = 50 mm), major diameter of bed (ØL = 14,4 cm) and lower height of bed (H L = 21, 5 cm). Under these geometric conditions, after 81 minutes of processing, the draft-tube LFTS achieved a concentration of saponins (0.0325%) and a saponins removal efficiency of 52.64%. At higher linear air inlet velocities and higher grain cycle frequencies, better efficiencies of saponin removal and lower residual concentrations of saponins in the grain are obtained. In general, it can be concluded that to obtain minimum residual concentrations of saponins in the grains and removal efficiencies greater than 90%, any configuration that generates linear air inlet velocities of 1 000 to 1 300 ms-1 and frequencies of 20 CPM will be appropriate. Lower grain circulation mass flows in draft-tube spouted beds, compared to those obtained in conventional spouted beds, generate a lack of uniformity in the removal of saponins in the treated grains and lower efficiencies.
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Vol. 19, No. 1