Thesis CALORIMETRIC STUDY OF RENEWABLE FUELS WITH THE SENSIBLE HEAT CALIMETRI APPARATUS
Date
2016
Authors
VOLKWEIN BARREDA, CHRISTOPHER HANNIE
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Abstract
La biomasa se usa comúnmente en Chile como materia prima para calderas para producir energía. Algunosempresas vinculadas a la producción y gestión de recursos forestales, utilizan sus desechos de maderay otros suministros de biomasa para la producción de energía. Estas plantas de energía son comúnmenteubicado en el sur de Chile, donde el clima beneficia el crecimiento de los árboles pero también aumentael contenido de humedad de la biomasa. Las empresas utilizan diferentes mezclas de biomasa con alta ycontenido de humedad variable para suministrar sus calderas. Este estudio tiene como objetivo caracterizar elbiomasa utilizada por Celulosa Arauco S.A. para la producción de energía. Celulosa Arauco S.A. esuna compañía que produce y maneja recursos forestales renovables y también está involucrada enla industria de generación de energía eléctrica. La biomasa se caracteriza comúnmente por el calorde combustión, distribuciones de tamaño de partícula, composición próxima, fundamental elemental yanálisis elemental de cenizas (Demirbas, 2004). En este estudio un estudio colorimétrico sobre la biomasaMezcla utilizada por Celulosa Arauco S.A. en la planta de energía Arauco se lleva a cabo. El analisisincluye diferentes escenarios donde ocho mezclas con diferentes composiciones de biomasa a las treslos diferentes contenidos de humedad son probados. El análisis colorimétrico incluye la determinaciónde los siguientes parámetros: tasas máximas de liberación de calor, tiempos de retardo de encendido, tiempo de encendido yel calor de combustión efec- tivo de cada mezcla en cada contenido de humedad. El estudio es tambiéndestinado a predecir la eficiencia de la combustión de cada tipo de biomasa en la caldera. PromedioSe encontraron eficiencias entre 30% y 50% para el aserrín, corteza de pino y astillas de maderaen el contenido de humedad original. Se encontraron eficiencias promedio entre 45% y 68%en las muestras con menos contenido de humedad Y eficiencias promedio entre 62% y 73% se encontraron en las muestras con los contenidos de humedad más bajos. Las astillas de madera registraron eltasa de liberación de calor pico promedio más alta en el contenido de humedad original, seguido de pinoladrar. Disminuir el contenido de humedad al siguiente nivel mejora significativamente larendimiento de la corteza de pino, informando de altas mejoras en la liberación media de calor picotasa de las muestras compuestas principalmente de este tipo de biomasa. Secando toda la biomasase mezcla durante un día a temperatura ambiente, la tasa promedio de liberación máxima de calor de todoslas mezclas aumentan en un 60% y el tiempo de retardo de encendido disminuye en un 50%. En orden para realizartodos los experimentos descritos anteriormente, un calorímetro ha sido diseñado, construido y validado. El calorímetro se llama Aparato de Calorimetría de Calor Sensible (SCALA).El calorímetro se compone principalmente de los siguientes componentes: una combustióncámara, donde se colocan las muestras, un ventilador que proporciona el aparato con una constanteflujo de aire ajustable, calentadores radiantes que suministran la muestra con un ajuste constanteflujo de calor incidente, un equilibrio de precisión que mide la pérdida de masa de la muestra, un ajusteInstrumento de espectroscopía láser de diodo (TDLAS) que mide las concentraciones de oxígenode los gases de salida en el conducto de escape y termopares
Biomass is commonly used in Chile as feedstock for boilers to produce energy. Somecompanies linked to forest resources production and management, uses their wood wastesand other biomass supplies for energy production. These power plants are commonlylocated in the south of Chile, where the climate benefits the trees growth but also increasesthe biomass moisture content. Companies use dierent biomass mixes with high andvariable moisture content to supply their boilers. This study is aimed to characterize thebiomass used by Celulosa Arauco S.A. for energy production. Celulosa Arauco S.A. isa company that produce and manage renewable forest resources and also is involved inthe electric energy generation industry. Biomass in commonly characterized by the heatof combustion, particle size distributions, proximate composition, ultimate elemental andash elemental analysis (Demirbas, 2004). In this study a calorimetric study on the biomassmix used by Celulosa Arauco S.A. in the power plant Arauco is carried out. The analysisincludes dierent scenarios where eight mixes with dierent biomass compositions at threedierent moisture contents are tested. The calorimetric analysis includes the determinationof the following parameters: peak heat release rates, ignition delay times, flaming time andthe eective heat of combustion of each mix at each moisture content. The study is alsoaimed to predict the combustion eciency of each type of biomass in the boiler. Averageeciencies between 30 % and 50 % were found for the sawdust, pine bark and wood chipsat the original moisture content. Average eciencies between 45 % and 68 % were foundin the samples with less moisture content. And average eciencies between 62 % and 73% were found in the samples with the lowest moisture contents. Wood chips registered thehighest average peak heat release rate at the original moisture content, followed by pinebark. Decreasing the moisture content to the following level improves significantly theperformance of pine bark, reporting high improvements in the average peak heat releaserate of the samples composed mostly of this type of biomass. By drying all biomassmixes during one day at ambient temperature, the average peak heat release rate of allmixes increase in 60 % and the ignition delay time decrease in 50 %. In order to performall the experiments described above, a calorimeter has been designed, constructed and validated. The calorimeter is called the Sensible Heat Calorimetry Apparatus (SCALA).The calorimeter is principally composed of the following components: a combustionchamber, where the specimens are placed, a fan that provides the apparatus with a constantadjustable air flow, radiant heaters that supplies the specimen with a constant adjustableincident heat flux, a precision balance that measures the mass loss of the sample, a TunableDiode Laser Spectroscopy (TDLAS) instrument that measures the oxygen concentrationsof the outlet gases at the exhaust duct, and thermocouples that measure the temperatureat dierent points. This calorimeter uses three dierent methods to determine the heatrelease rate (HRR) of a burning specimen; the sensible enthalpy rise (SER) method, theoxygen consumption (OC) method and the mass loss rate (MLR) method. The maindierence between this calorimeter and other standard calorimeters is that the SCALAuses the TDLAS technique to measure the oxygen concentrations of the outlet gases. Thistechnique avoids the use of filters to perform the oxygen concentrations measurementsand thus reduces the apparatus response time. The principle of operation, the methodsto determine the heat release rates and the calibrations procedures are established anddescribed in this study. The calorimeter is experimentally validated using PMMA. Theresults obtained with the three methods are compared between them. Agreement betweenthe three techniques is achieved. The results are compared with other results obtainedwith the standard calorimeter Fire Propagation Apparatus (FPA). There was agreementbetween the results obtained with the SCALA and the FPA. The SCALA enthalpy risemethod showed to achieve better results than the sensible enthalpy rise method performedby the FPA. The OC method achieved good agreement but reported the highest magnitudes.The uncertainty of the OC and the SER results are calculated in function of the HRR. Thetotal relative uncertainty of the oxygen consumption HRR calculations vary between 10% and 85 %, where 10% correspond to 16 kW and 85 % correspond to 0:5 kW. The totalrelative uncertainty of the sensible enthalpy rise HRR calculations vary between 4 % and23 %, where 4% correspond to 16 kW and 23 % correspond to 0:5 kW.
Biomass is commonly used in Chile as feedstock for boilers to produce energy. Somecompanies linked to forest resources production and management, uses their wood wastesand other biomass supplies for energy production. These power plants are commonlylocated in the south of Chile, where the climate benefits the trees growth but also increasesthe biomass moisture content. Companies use dierent biomass mixes with high andvariable moisture content to supply their boilers. This study is aimed to characterize thebiomass used by Celulosa Arauco S.A. for energy production. Celulosa Arauco S.A. isa company that produce and manage renewable forest resources and also is involved inthe electric energy generation industry. Biomass in commonly characterized by the heatof combustion, particle size distributions, proximate composition, ultimate elemental andash elemental analysis (Demirbas, 2004). In this study a calorimetric study on the biomassmix used by Celulosa Arauco S.A. in the power plant Arauco is carried out. The analysisincludes dierent scenarios where eight mixes with dierent biomass compositions at threedierent moisture contents are tested. The calorimetric analysis includes the determinationof the following parameters: peak heat release rates, ignition delay times, flaming time andthe eective heat of combustion of each mix at each moisture content. The study is alsoaimed to predict the combustion eciency of each type of biomass in the boiler. Averageeciencies between 30 % and 50 % were found for the sawdust, pine bark and wood chipsat the original moisture content. Average eciencies between 45 % and 68 % were foundin the samples with less moisture content. And average eciencies between 62 % and 73% were found in the samples with the lowest moisture contents. Wood chips registered thehighest average peak heat release rate at the original moisture content, followed by pinebark. Decreasing the moisture content to the following level improves significantly theperformance of pine bark, reporting high improvements in the average peak heat releaserate of the samples composed mostly of this type of biomass. By drying all biomassmixes during one day at ambient temperature, the average peak heat release rate of allmixes increase in 60 % and the ignition delay time decrease in 50 %. In order to performall the experiments described above, a calorimeter has been designed, constructed and validated. The calorimeter is called the Sensible Heat Calorimetry Apparatus (SCALA).The calorimeter is principally composed of the following components: a combustionchamber, where the specimens are placed, a fan that provides the apparatus with a constantadjustable air flow, radiant heaters that supplies the specimen with a constant adjustableincident heat flux, a precision balance that measures the mass loss of the sample, a TunableDiode Laser Spectroscopy (TDLAS) instrument that measures the oxygen concentrationsof the outlet gases at the exhaust duct, and thermocouples that measure the temperatureat dierent points. This calorimeter uses three dierent methods to determine the heatrelease rate (HRR) of a burning specimen; the sensible enthalpy rise (SER) method, theoxygen consumption (OC) method and the mass loss rate (MLR) method. The maindierence between this calorimeter and other standard calorimeters is that the SCALAuses the TDLAS technique to measure the oxygen concentrations of the outlet gases. Thistechnique avoids the use of filters to perform the oxygen concentrations measurementsand thus reduces the apparatus response time. The principle of operation, the methodsto determine the heat release rates and the calibrations procedures are established anddescribed in this study. The calorimeter is experimentally validated using PMMA. Theresults obtained with the three methods are compared between them. Agreement betweenthe three techniques is achieved. The results are compared with other results obtainedwith the standard calorimeter Fire Propagation Apparatus (FPA). There was agreementbetween the results obtained with the SCALA and the FPA. The SCALA enthalpy risemethod showed to achieve better results than the sensible enthalpy rise method performedby the FPA. The OC method achieved good agreement but reported the highest magnitudes.The uncertainty of the OC and the SER results are calculated in function of the HRR. Thetotal relative uncertainty of the oxygen consumption HRR calculations vary between 10% and 85 %, where 10% correspond to 16 kW and 85 % correspond to 0:5 kW. The totalrelative uncertainty of the sensible enthalpy rise HRR calculations vary between 4 % and23 %, where 4% correspond to 16 kW and 23 % correspond to 0:5 kW.
Description
Catalogado desde la version PDF de la tesis.
Keywords
BIOMASA , CALOR DE COMBUSTION EFECTIVO , CALORIMETRIA , CALORIMETRO , TASA DE LIBERACION DE CALOR