Effects of pyrolysis atmosphere on the porous structure and reactivity of chars from middle and high rank coals
Efectos de la atmósfera de pirólisis sobre la estructura porosa y la reactividad de los carbonizados formados desde carbones de alto y mediano rango
Keywords:
Slow pyrolysis, Pore size distribution, large coal particles, Oxy-combustion, Reactivity (en)Pirólisis lenta, distribución de tamaño de poro, grandes partículas de carbón, Oxy-combustión, reactividad (es)
Se estudió la influencia de una atmósfera basada en CO2 o N2 sobre la estructura porosa y la microestructura de carbonizados de carbón obtenidos de la pirólisis lenta no isotérmica desde temperatura ambiente hasta 900 °C de dos carbones de diferente rango (Semi-Antracita (SA) y Bituminosos Alto en Volátiles tipo C (BAVC)), y de diferentes distribuciones de tamaño de partícula. Para todos los carbonizados se realizó la caracterización fisicoquímica (Análisis ultimo y próximo), la caracterización morfológica y estructural por combinación de técnicas como espectroscopia Rama, Microscopia electrónica de barrido por emisión de campo (FE-SEM), área superficial (BET - Brunauer-Emmett-Teller) y volumen y diámetro de microporos por mediciones de adsorción en CO2 (Horvath-Kawazoe (HK) method). Se encontró que los parámetros cinéticos, las propiedades fisicoquímicas y la reactividad de los carbonizados de carbón son diferentes dependiendo de la atmósfera de pirólisis. También se determinó que para el carbonizado de carbón de SA, con un tamaño de partícula mayor de 0,7mm, la superficie BET aumenta cuando la atmósfera se enriquece en CO2. Este efecto parece ser promovido por la interacción de diferentes procesos como las reacciones secundarias intrapartícula (ablandamiento, nucleación y coalescencia de burbujas, entrecruzamiento, entre otros), diferencias en la difusividad térmica de N2 y CO2, y los efectos reactivos de este último. Además, los ensayos de reactividad oxidativa de los sólidos mostraron que el carbonizado formado en una atmósfera de CO2 es más reactivo que el formado en N2. Con los resultados del análisis de Raman y los parámetros cinéticos cuantificados, se concluyó que la atmósfera de reacción determinó el grado de ordenación alcanzado por la estructura carbonosa y que las propiedades termo-difusivas de la atmósfera de reacción promovieron diferencias estructurales en el carbonizado, incluso a bajas velocidades de calentamiento.
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