Estudio de cinética en procesos termogravimétricos de materiales lignocelulósicos

La madera de pino representa el 20% de las especies forestales plantadas en todo el mundo, y actualmente es de vital importancia en aplicaciones industriales como en aserrío, fabricación de papel y medicina. Actualmente, se ha destacado su uso en aplicaciones energéticas. En este estudio se presenta una breve revisión sobre el análisis térmico realizado a diversas especies de madera de pino. Nos enfocamos principalmente al análisis de los resultados respecto a cómo varía el contenido de masa o pérdida de peso con el cambio de temperatura a partir del análisis de las curvas de termogravimetría y su derivada. Se han considerado diversas especies de madera de pino: Pinus caribaea, Pinus patula, Cupressus sempervirens, Pinus pinaster, Pinus radiata, Pinus sylvestris, Pinus pinea y Pinus taeda. Con el objetivo de mostrar las diferencias y similitudes respecto a la estabilidad térmica de las especies mencionadas, se han discutido los principales parámetros a partir de las curvas de termogravimetría como energía de activación, factor pre-exponencial y orden de reacción. Además, se examinan las etapas de descomposición de acuerdo a los principales componentes de la madera tales como agua, celulosa, hemicelulosa, lignina y extractivos. Pine wood accounts for 20% of the world's planted forest species, and is currently of vital importance in industrial applications such as sawmills, papermaking and medicine. Actually, its use in energy applications has been emphasized. This study presents a brief review on the thermal analysis of various species of pine wood. We focus mainly on the analysis of the results regarding how the mass content or weight loss varies with the temperature change from the analysis of the thermogravimetric curves and its derivative. Several species of pine wood have been considered: Pinus caribaea, Pinus patula, Cupressus sempervirens, Pinus pinaster, Pinus radiata, Pinus sylvestris, Pinus pinea and Pinus taeda. In order to show the differences and similarities with respect to the thermal stability of the mentioned species, we have discussed the main parameters from the thermogravimetry curves such as activation energy, pre-exponential factor and reaction order. In addition, the decomposition stages are examined according to the main components of the wood such as water, cellulose, hemicellulose, lignin and extractives

Chemical Composition and Energy Evaluation of Abies spp. and Pinus spp. Sawdust Collected as a Byproduct of the Primary Wood Sawing

The aim of this paper is to chemically evaluate the byproducts of the primary processing of genera Abies and Pinus, to determine the possibility of using them as solid biofuel. Ash percentage, volatile matter and fixed carbon values were determined by proximate analysis. The basic chemical composition includes the determination of extractives content, lignin and holocellulose. Ash microanalysis was performed with an X-ray spectrometer and the calorific value of the samples was determined by using an AC600 calorimeter. The results of this research varied as follows: the content of inorganic substances (0.33% to 0.41%), volatile matter (88.54% to 82.57%), fixed carbon (11.13% to 17.06%), extractives content (5.37% to 17.82%), Runkel lignin (27.33% to 30.97%), holocellulose content (58.53% to 69.56%) and calorific value (19.09 MJ·kg-1 to 20.42 MJ·kg-1). According to the X-ray analysis, the most abundant elements were potassium, calcium and magnesium; whereas no heavy metals were found. The results of this research show that the two genera studied here are suitable for solid biofuel production

CELDAS DE COMBUSTIBLE COMO ELEMENTOS POTENCIADORES PARA UN DESARROLLO ENERGÉTICO SUSTENTABLE

Las celdas de combustible generan electricidad y calor durante la reacción electroquímica que ocurre entre el oxígeno e hidrógeno para formar agua. La tecnología de la celda de combustible es un camino prometedor para proporcionar energía en áreas rurales, donde no hay acceso a la red eléctrica pública, o donde hay un costo enorme en el cableado y transferencia de electricidad. Además, las celdas de combustible, pueden emplearse como fuente de energía, para asegurar la energía eléctrica, por ejemplo, en fuentes de potencia ininterrumpidas, estaciones de generación de energía y sistemas de distribución. En este artículo, se hace un estudio comparativo sobre diseño básico, principios de funcionamiento, aplicaciones, ventajas y desventajas de las diversas tecnologías disponibles para celdas de combustible. Además, se comparan las características tecno-económicas de los vehículos que funcionan con celdas de combustible a partir de hidrógeno y vehículos con motor de combustión interna. Los resultados indican que los sistemas de celdas de combustibles tienen un diseño simple, confiabilidad alta, funcionamiento silencioso, alta eficiencia y menor impacto ambiental. El objetivo de este artículo, es servir de una conveniente referencia sobre la generación de energía a partir de las celdas de combustible

Adsorción de amoniaco en carbón activado de Pinus Tropicalis de Pinar del Río

The accumulation of forest residues in sawmills and other industrial sites of wood processing, can become a polluting center and a possible source of fire, which will always be harmful to society. For this reason, the creation of a product of great importance such as activated carbon, converts sawdust into raw material with added value. This led us to consider the objective of determining the possibilities of activated carbon with phosphoric acid, obtained from sawdust of tropicalis pine, for the adsorption of ammonia vapors, which is a possible exhaust contaminant in different Cuban industries. For the characterization of the coals, the influence of the acid concentration, impregnation ratio and activation temperature on the development of the porous structure measured by the iodine technique was determined. In addition to the selected biomass, it was experimented with sawdust of pine caribaea var. Caribaea, by way of comparison, both from the province of Pinar del Río, Cuba. Experiments showed that activation with phosphoric acid with a concentration of 40% and activation temperature of 500 °C, produces an activated carbon with good properties for the adsorption of ammonia vapors, as well as good iodine index values. For an acid concentration of 40%, activation temperature of 500 °C and an impregnation ratio of 2, the best results were obtained in iodine index values and adsorption of ammonia vapors.Los residuos forestales del procesamiento de la madera, son contaminantes y fuentes de posibles incendios, perjudicial para la sociedad. Por tal razón la creación de un producto de gran importancia como es el carbón activado, convierte al aserrín en materia prima con valor agregado. Esto condujo a plantear el objetivo de determinar las posibilidades del carbón activado con ácido fosfórico, obtenido del aserrín de pinus tropicalis, para la adsorción de vapores de amoniaco, el cual es un posible contaminante por escape en diferentes industrias cubanas, lo cual constituye un problema a resolver. Para la caracterización de los carbones, se determinó la influencia de la concentración del ácido, relación de impregnación y temperatura de activación en el desarrollo de la estructura porosa medida por la técnica de yodo. Además de la biomasa seleccionada, se experimentó con aserrín de pinus caribaea Morelet var. Caribaea, a modo de comparación, ambos de la provincia de Pinar del Río, Cuba. Los experimentos mostraron que la activación con ácido fosfórico con concentración de 40 % y temperatura de activación de 500 °C, se produce un carbono activado con buenas propiedades para la adsorción de vapores de amoníaco, así como buenos valores de índice de yodo. Para una concentración del ácido de 40 %, temperatura de activación de 500 ºC y una relación de impregnación de 2, se obtuvieron los mejores resultados en valores de índice de yodo y adsorción de vapores de amoniaco. Los resutados de pinus tropicalis fueron superiores a los de pinus caribaea

Efecto de la intemperización y proceso en las características físicas, mecánicas y energéticas de briquetas

Las industrias forestales generan residuos de aserrín que son subutilizados, frecuentemente estos se acumulan durante años, lo que puede propiciar incendios y contaminación. Los objetivos de la presente investigación fueron comparar las propiedades energéticas entre el aserrín fresco e intemperizado de la madera de Pinus pseudostrobus, y determinar algunas propiedades físicas y mecánicas de briquetas elaboradas a partir de ellos. El aserrín se caracterizó según su distribución granulométrica, contenido de humedad, material volátil, cenizas y carbono fijo, de acuerdo con las normas europeas UNE-EN14774-3 y UNE-EN14775. Las briquetas se elaboraron en una máquina marca LIPPEL a presiones de 10 y 15 MPa, y temperaturas de 50, 70 y 90 ºC; su calidad se determinó mediante análisis proximales, propiedades físicas y mecánicas. Los valores medios y errores estándares se calcularon a las variables: tipo de aserrín, presión y temperatura. Los datos se analizaron estadísticamente como bloques completos al azar y se realizaron análisis de varianza para determinar la existencia de diferencias estadísticas (p<0.05) entre tratamientos. Cuando las hubo, se hicieron pruebas de Tukey. El aserrín intemperizado mostró mejores propiedades energéticas, al presentar menor porcentaje de humedad (9.12 %) y mayor contenido de carbono fijo (13.84 %); sin embargo, presentó un porcentaje superior de cenizas (0.84 %). Las briquetas con mejor calidad se obtuvieron cuando se utilizó aserrín fresco a 15 MPa de presión y temperatura de 70 °C

Chemical and Energetic Properties of Seven Species of the Fabaceae Family

In this work, the chemical compositions and energetic properties of the wood and bark of seven Fabaceae species were determined to evaluate their dendroenergetic potential. Chemical composition, elemental, proximate and heating value analyses were conducted. In addition, an ash microanalysis was performed. The obtained results varied as follows: cellulose (from 20.21% in Parkinsonia aculeate bark to 58.83% in Albizia plurijuga sapwood), hemicelluloses (from 8.81% in Eysenhardia polystacya heartwood to 23.71% in Pakinsonia aculeate wood), lignin (from 12.88% in wood to 26.53% in bark of Parkinsonia aculeate), extractives (from 11.68% in sapwood to 36.17% in bark of Eysenhardia polystacya), carbon (from 42.4% in Albizia plurijuga bark to 49.5% in Eysenhardtia polystacya heartwood), hydrogen (from 6.4% in Eysenhardtia polystacya bark to 7.3% in Albizia plurijuga sapwood), oxygen (from 42.3% in Prosopis laevigata bark to 50.5% in Acacia pennatula bark), nitrogen (from 0.11% in Albizia plurijuga heartwood to 1.64% in Prosopis laevigata bark), sulfur (from 0.04% in Prosopis laevigata heartwood to 0.14% in Acacia farnesiana wood, Erythina caralloides bark, and Prosopis laevigata bark), ash (from 0.76% in Eysenhardtia polystacya heartwood to 11.49% in Acacia plurijuga bark), volatile material (from 70.08% in Eysenhardtia polystacya bark to 91.75% in Albizia plurijuga sapwood), fixed carbon (from 6.97% in Albizia plurijuga sapwood to 23.44% in Prosopis laevigata bark), and calorific value (from 17.36 MJ·kg-1 in Acacia pennatula bark to 21.23 MJ·kg-1 in Prosopis laevigata bark). The most abundant chemical elements in wood ash and bark ash are listed here: Ca˃K˃P˃Mg˃Na. According to the obtained results, the wood and bark of the seven Fabaceae species could be used to produce solid biofuels for local use. Additionally, highlighting the high concentrations of extractives was important, especially in the bark samples, which could be a potential source of phytochemicals

Comparison of five pretreatments for the production of fermentable sugars obtained from Pinus pseudostrobus L. wood

To benefit from the use of a waste product such as pine sawdust from a sawmill in Michoacán, Mexico, five different pretreatments for the production of reducing sugars by enzymatic hydrolysis were evaluated (sodium hydroxide, sulfuric acid, steam explosion, organosolv and combined method nitric acid / sodium hydroxide). The main finding of the study was that the pretreatment with 6 % HNO3 and 1 % NaOH led to better yields than those obtained with sodium hydroxide, dilute sulfuric acid, steam explosion, and organosolv pretreatments. Also, HNO3 yields were maximized by the factorial method. With those results the maxima concentration of reducing sugar found was 97.83 ± 1.59, obtained after pretreatment with 7.5 % HNO3 at 120 °C for 30 minutes; followed by 1 % of NaOH at 90 °C for 30 minutes at pH 4.5 for 168 hours with a load enzyme of 25 FPU/g of total carbohydrates. Comparing the results obtained by the authors with those reported in the literature, the combined method was found to be suitable for use in the exploitation of sawdust

Use of agave durangensis bagasse fibers in the production of wood-based medium density fiberboard (MDF)

There is an increasing interest in using non-wood lignocellulosic materials for the production of wood-based medium density fiberboard (MDF). Agave durangensis Gentry bagasse is a waste product produced in large quantities in the mezcal industry. This study evaluated the incorporation of A. durangensis bagasse fibers (ADBF) to elaborate MDF wood-based panels. Three types of panels with different ratios (wood fibers: bagasse fibers) were investigated. The ratios evaluated were 100:0, 90:10, and 70:30. The density profiles, water absorption, and thickness swell of the panels were determined, as well as the modulus of elasticity (MOE), modulus of rupture (MOR), and internal bond (IB), according to the ASTM D1037-06a standard. The results were compared to the ANSI A208.2-2016 standard. The effect of the addition of ADBF on the properties of the panels was analyzed. Density profiles were comparable among the three types of panels, while water absorption, thickness swelling, MOE, MOR, and IB were similar between panels with ratios of 100:0 and 90:10. Panels with 10% and 30% of ADBF meet the minimum ANSI requirements for quality grade 115. It is feasible to use up to 30% of ADBF in the manufacture of wood-based MDF panels

Assessing the natural durability of different tropical timbers in soil-bed tests

Ground contact speeds up timber decay because of the large number of microorganisms in soil. This study, we assessed the natural durability of seven tropical species using the European standard EN 807 (2001). We embedded samples of Dalbergia granadillo, Cordia elaeagnoides, Swietenia humillis, Tabebuia donell-smithii, Hura polyandra, Enterolobium cyclocarpum and Tabebuia rosea and temperate species Fagus sylvatica (as a control) in sandy, clay-sandy-loam and clay-loam for 8, 16, 24 and 32 weeks. We evaluated durability of the samples by determining the mass loss and modulus of elasticity (MOE) loss. The results varied significantly (p &lt; 0.001) depending on timber species and soil type considered. The D. granadillo and C. elaeagnoides were the most durable, with mass losses of 4.5%, 6.5% and MOE losses of 4.5%, 20.5%, respectively. F. sylvatica, T. rosea and E. cyclocarpum samples were the least durable, with mass losses of 22.3-25% and MOE losses of 35.8-59.8%, respectively. Decay was most aggressive in sandy-clay-loam soil followed by the clay-loam soil and finally the sandy soil

Physical, mechanical and energy characterization of wood pellets obtained from three common tropical species

ABSTRACT Background. The need for energy sources with low greenhouse gas emissions and sustainableproductionencouragesthesearchforalternativebiomasssources.However, the use of biomass fuels faces the problem of storage, transport and lower energy densities.Low-densityvaluescannegativelyaffectenergydensity,leadingtoanincrease intransportationandstoragecosts.Useofpelletsasalternativebiomasssourceisaway toreducethevolumeofbiomassbydensification,whichimprovestheirenergyquality. They are produced by diverse biomass resources and mainly from wood materials. In allcases,itisimportanttoevaluatethefuelcharacteristics,todeterminetheirsuitability on the heating system and handling properties. Methods. The present study determines and compares data from proximate analysis, calorific values, physical and mechanical properties of wood pellets produced from the common tropical species Acaciawrightii, Ebenopsisebano and Havardiapallens. Data were obtained from pellets produced from each species chips collected from an experimentalplantationandanalyzedthroughANOVAandKruskal–Wallistestat0.05 significance level. Results.Theresultsofdiameter,lengthandlength/diameterratiodidn’tshowstatistical differences (p > 0.05) among species. Acaciawrightii showed the highest density (1.2 g/cm3). Values on weight retained and compression test showed statistical differences(p=0.05)amongspecies.Havardiapallenswasmoreresistanttocompression strength than A.wrightii and Ebenopsisebano. Statistical differences (p<0.01) were alsoobservedforthevolatilematterandcalorificvalue.E.ebanohasthelowestvolatile matter (72%), highest calorific value (19.6 MJ/kg) as well as the fixed carbon (21%). Discussion.Thepelletsofthespeciesstudiedhaveahighenergydensity,whichmakes themsuitableforbothcommercialandindustrialheatingapplications.Apelletwithlow compression resistance tends to disintegrate easily, due to moisture adsorption. The percentages obtained for the resistance index were higher than 97.5%, showing that the pellets studied are high-quality biofuels. Proximate analysis values also indicate good combustion parameters. Pellets ofAcaciawrightii and Ebenopsisebano are the morefavorablerawmaterialsourcesforenergypurposesbecauseoftheirhighdensity, calorific value, low ash content and they also met majority of the international quality parameters