4,587 research outputs found
Agricultural bio-char production, renewable energy generation and farm carbon sequestration in Western Australia: Certainty, uncertainty and risk
No full textReducing the vulnerability of agriculture to climate change while increasing primary productivity requires mitigation and adaptation activities to generate profitable co-benefits to farms. The conversion of woody-wastes by pyrolysis to produce bio-char (biologically derived charcoal) is one potential option that can enhance natural rates of carbon sequestration in soils, reduce farm waste, and substitute renewable energy sources for fossil-derived fuel inputs. Bio-char has the potential to increase conventional agricultural productivity and enhance the ability of farmers to participate in carbon markets beyond traditional approach by directly applying carbon into soil. This paper provides an overview of the pyrolysis process and products and quantifies the amount of renewable energy generation and net carbon sequestration possible when using farm bio-waste to produce bio-char as a primary product. While this research provides approximate bio-char and energy production yields, costs, uses and risks, there is a need for additional research on the value of bio-char in conventional crop yields and adaptation and mitigation options
A Conversation with Char Booth
No full textWelcome to a special audio edition of In the Library with the Lead Pipe. Ellie Collier talks to Char Booth, E-Learning Librarian at the University of California at Berkeley and author of Informing Innovation: Tracking Student Interest in Emerging Library Technologies at Ohio University, a book length research report recently published by ACRL and available [...
Cinética da gaseificação do bagaço de laranja e serragem de madeira com CO2
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2013.A valorização de resíduos agroindustriais por meio de processos de conversão termoquímica para a produção de energia apresenta vantagens econômicas e ambientais. Dada suas propriedades físico-químicas e disponibilidade, o bagaço de laranja é um resíduo com grande potencial para seu uso como fonte de energia. A gaseificação deste tipo de resíduo apresenta vantagens devido ao seu alto teor de minerais que atuam como catalisadores da reação, convertendo a matéria orgânica em temperaturas menores em comparação com outras biomassas. Neste trabalho, amostras de bagaço de laranja (BL), serragem de madeira (SM), e suas misturas foram gaseificadas a fim de comparar suas reatividades com CO2. Inicialmente, os resíduos carbonosos da pirólise (char) do BL, SM, e misturas foram obtidos por meio da pirólise das amostras em um reator de quartzo de leito fixo à temperatura de 1173 K e tempo de residência de 15 minutos em atmosfera de N2. As biomassas e char de biomassas foram caracterizadas quanto às suas propriedades físico-químicas. Após a pirólise foram obtidos sólidos com maiores área superficiais e teor de carbono. A análise do teor de potássio nas cinzas do char do BL permitiu determinar que este mineral não foi volatilizado durante a pirólise e teria influência sobre sua reatividade. A reação de gaseificação com CO2 puro foi realizada em um analisador termogravimétrico sob condições isotérmicas e não isotérmicas. No caso isotérmico, as reações químicas foram realizadas na faixa de temperatura entre 1003-1123K para o BL e 1123-1223 K para a SM. No caso dos testes não isotérmicos a amostra foi aquecida desde temperatura ambiente até 1253 K e taxas de aquecimento de 10, 20, e 30 K/min. As reações foram realizadas em um reator diferencial e em condições que os efeitos de transferência de massa e calor foram desprezíveis. Os resultados obtidos demonstraram uma maior reatividade para o BL com CO2 em comparação à SM isto devido à influência dos minerais alcalinos, em particular o teor de potássio presente em alta concentração nas amostras do BL. Foi estudado o efeito da inibição do CO sobre a taxa da reação de gaseificação do BL pelo método isotérmico. Os dados experimentais ajustaram-se bem ao modelo de Langmuir Hinshelwood mostrando boa representatividade. Estudou-se o efeito da adição do BL sobre a reatividade da SM com CO2 puro, verificando-se uma diminuição da taxa de reação de gaseificação.Abstract : Agriculture waste valorization through thermochemical conversion processes for energy production has economic and environmental advantages. Given its physicochemical properties and availability, orange bagasse is a residue with great potential for its use as an energy source. Gasification of these wastes has advantages because they have a high content of minerals which act as catalysts of reactions, converting organic matter at lower temperatures compared to other biomass. In this work, samples of orange bagasse (BL) and sawdust (SM) were gasificated in order to compare their reactivity with CO2. Initially, the pyrolysis carbon residue (char) from the BL and SM were obtained through the pyrolysis of samples in a quartz reactor fixed bed at temperature of 1173 K and residence time of 15 minutes under N2. The biomass char and biomass were characterized according to their physicochemical properties. Solids with higher surface area and carbon content were obtained. The analysis of the potassium content in the ashes of the char BL determined that this mineral was not volatilized during pyrolysis and would have influence on its reactivity. The gasification reaction with pure CO2 was performed in a thermogravimetric analyzer under isothermal and non isothermal conditions. In the isothermal case the chemical reactions were performed in the temperature range of 1003-1123K for the BL and 1123-1223 K for SM. In the case of non-isothermal tests, samples were heated from room temperature to 1253 K and heating rates of 10, 20, and 30 K/min. The reactions were performed in a differential reactor conditions and the effects of heat and mass transfer were negligible. The results showed greater reactivity to the BL with CO2 as compared to SM this due to the influence of alkaline minerals, particularly the potassium content present in high concentration in the samples of BL. It was determined the effect of inhibition by CO of BL gasification reaction using the isothermal method. Experimental data have fit well to the Langmuir Hinshelwood model. It was studied the effect of adding BL on the reactivity of SM with pure CO2 verifying a decrease of the reaction rate of gasification
Redução direta do monóxido de nitrogênio com coque
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia QuímicaUm dos poluentes atmosféricos mais significativos em processos de combustão de carvão são os óxidos de nitrogênio, onde 95% se apresentam como monóxido de nitrogênio. O nitrogênio quimicamente ligado no carvão é responsável por mais de 80% do NOX total. Como tem sido constatado, o NO formado pela oxidação do nitrogênio do coque pode ser reduzido pelo próprio coque para resultar N2. Enquanto as reações homogêneas de formação do NO são bem conhecidas, a conversão heterogênea do nitrogênio retido no coque, para formar NO, é pouco entendida. O objetivo deste trabalho foi estudar a reação de redução do NO em N2 e CO2, utilizando como redutor, três amostras diferentes de coque. Os coques foram obtidos a partir da pirólise de três carvões minerais em um reator de aço a 873 K, em atmosfera inerte. As reações foram realizadas em um reator diferencial de aço de fluxo em leito fixo. O gás reagente utilizado foi uma mistura padrão de 5,0% de NO em He. Os gases de entrada e saída do reator foram analisados por cromatografia gasosa, e a conversão do NO determinada em termos de N2 formado. Os carvões utilizados foram caracterizados, determinando-se suas composições químicas e estruturais. As variáveis investigadas para estudo da reatividade dos coques foram: concentração do NO no gás de alimentação do reator (2,0, 4,0, e 5,0%), e temperatura (523 K - 673 K). A medida da reatividade foi determinada em termos de conversão de NO em N2. A ordem global da reação de redução relativa ao NO foi 1. As energias de ativação aparentes para a pressão parcial de 0,05 atm foi de 10,58 kcal.mol-1 para a amostra do carvão 1 A, 7,92 kcal.mol-1 para a amostra do carvão 2 B, e 8,20 kcal.mol-1 para a amostra do carvão CBB FLT. As baixas energias de ativação podem ser atribuídas ao efeito catalítico devido à presença de metais na matéria mineral do carvão. Os dados experimentais também se ajustaram bem ao modelo de Langmuir-Hinshelwood. Nitrogen oxides are among the major atmospheric pollutants, where 95% of it appearing as nitric oxides. The fuel bond nitrogen is the major source of NO, accounting for more than 80% of the total NO. As has been previously stated, the NO formed by oxidation of the char nitrogen can be reduced by the char itself to yield N2. While some knowledge of the conversion of the volatile nitrogen to NOX via homogeneous mechanisms has been studied, the heterogeneous conversion of the nitrogen retained in the char is less well understood. The present work is concerned with the reduction of NO yielding N2 and CO2, using three different chars as the reducing agent. The char were obtained from mineral coal pyrolysis in a stell reactor at 873 K, in na inert atmosphere. The reactions were carried out in a fixed bed reactor. A 5.0% NO in He was passed dawnward through the reactor. The products analyses were made with gas chromatograph, and NO conversion was determined from formed N2. The samples were characterized, determining its chemical and structural composition. The investigated variables for the char reactivity study were: inlet NO concentration (2,0; 4,0 e 5,0%), and temperature (523 K # 673 K). The reduction reaction with NO is generally found to be first order. The apparent activation energy for the 0,05 atm partial pressure was 10.58 kcal.mol-1 for the 1 A sample, 7.92 kcal. mol-1 for the 2 B sample and 8.20 kcal.mol-1 for the CBB FLT char. The data are in agreement whit a Langmuir-Hinshelwood model
On certain submodules of Weyl modules for SO(2n+1,F) with char(F) = 2
No full textFor let be the Weyl module for the special orthogonal group G = \mathrm{SO}(2n+1,\F) with respect to the -th fundamental dominant weight of the root system of type and put . It is well known that all of these modules are irreducible when \mathrm{char}(\F) \neq 2 while when \mathrm{char}(\F) = 2 they admit many proper submodules. In this paper, assuming that \mathrm{char}(\F) = 2, we prove that admits a chain of submodules where for and is the trivial 1-dimensional module. We also show that for the quotient is isomorphic to the so called -th Grassmann module for . Resting on this fact we can give a geometric description of as a submodule of the -th Grassmann module. When \F is perfect G\cong \mathrm{Sp}(2n,\F) and is isomorphic to the Weyl module for \mathrm{Sp}(2n,\F) relative to the -th fundamental dominant weight of the root system of type . All irreducible sections of the latter modules are known. Thus, when \F is perfect, all irreducible sections of are known as well
Gaseificação de carvões nacionais com vapor de água visando a produção de gás de síntese
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2013.The steam gasification of Brazilian coal chars, subbituminous and bituminous, were investigated using a thermobalance in a temperature range of 1073-1173 K and pressure range of 1-20 bar. The operating variables used were in agreement with differential reactor and free diffusion limitations. The coal char samples were characterized, and the effects of temperature, total system pressure, parcial pressure and hidrogen on the kinetics of steam gasification were determined. The non-reactive core model was the one that best described the gasification reactions, at conditions studied, for conversions between 5-80%. For these coals and temperature range studied between 800 and 900 ° C, 1 bar, the activation energies were found to be 119.2 kJ?mol-1 and 170 kJ?mol-1 and pre-exponential factor were determined to be 4,10?105 e 4,55?103 min-1, respectively. Based on these parameters was determined the coal reactivity: CMRS-02 > CMSC-04 > CMSC-02 > CMSC-01. The higher reactivity for coal CMRS-02 was ascribed to the coal rank and vitrinite content. Regarding the effect of temperature, total pressure of the system and parcial pressure of steam on the reaction rate, the results showed that these effects were higher for bituminous coals, as the rank coal has more influence on the rate of reaction. The presence of hidrogen strongly inhibits the char-steam gasification reactions. The gases formed were H2, CO2and CO and the molar ratio H2/CO between 1,5 and 2 indicates that the syngas produced is promising for Fischer-Tropsch synthesis
Estudos da reatividade de coques de carvões catarinenses atraves da gaseificação com CO2
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro TecnologicoDiversas investigações a respeito da cinética da gaseificação têm sido realizadas para elaboração de projetos e construção de gaseificadores. Carvões e seus coques são materiais heterogêneos, complexos, e a descrição completa de todos os mecanismos físicos e químicos que controlam as reações de gaseificação ainda não são bem conhecidos, principalmente com relação aos carvões catarinenses. Esse trabalho teve por objetivo estudar a influência de dois tipos de carvão/coque sobre a cinética das reações de gaseificação. Os coques foram pirolisados a 1100ºC, em atmosfera inerte, a partir de dois carvões catarinenses. A reatividade destes coques foi determinada em CO2 (fluxo de 0,5 NI/mim) em um reator de aço 316 L a temperaturas de 900ºC a 975ºC, e uma pressão total de 1 atmosfera. Para se estudar a influência da pressão parcial do CO2 e o efeito do impedimento do produto CO sobre a velocidade de reação, um tipos de coque foi gaseificado com misturas de CO2/N2 e CO2/CO/N2. Para a discussão dos dados cinéticos foi utilizada uma equação de velocidade com ordem de reação n=1, relativa ao carbono como medida para a reatividade, a qual melhor descreveu o comportamento desses coques durante a gaseificação. Os dados experimentais dos sistemas CO2/N2-Coque e CO2/CO/N2-Coque, ajustaram-se bem a uma equação do tipo Langmuir-Hinshelwood. Na análise dos resultados foram considerados a influência do grau de conversão, superfície interna, matéria mineral dos carvões e modificações estruturais sofridas pelo tratamento ácido e pirólise
Effect of pyrolysis conditions on bone char characterization and its ability for arsenic and fluoride removal
No full textThis study examined arsenite [As(III)], arsenate [As(V)] and fluoride (F−) removal potential of bone char produced from sheep (Ovis aries) bone waste. Pyrolysis conditions tested were in the 500 °C–900 °C range, for a holding time of 1 or 2 h, with or without N2 gas purging. Previous bone char studies mainly focused on either low or high temperature range with limited information provided on As(III) removal. This study aims to address these gaps and provide insights into the effect of pyrolysis conditions on bone char sorption capacity. A range of advanced chemical analyses were employed to track the change in bone char properties. As pyrolysis temperature and holding time increased, the resulting pH, surface charge, surface roughness, crystallinity, pore size and CEC all increased, accompanied by a decrease in the acidic functional groups and surface area. Pyrolysis temperature was a key parameter, showing improvement in the removal of both As(III) and As(V) as pyrolysis temperature was increased, while As(V) removal was higher than As(III) removal overall. F− removal displayed an inverse relationship with increasing pyrolysis temperature. Bone char prepared at 500 °C released significantly more dissolved organic carbon (DOC) then those prepared at a higher temperature. The bone protein is believed to be a major factor. The predominant removal mechanisms for As were surface complexation, precipitation and interaction with nitrogenous functional groups. Whereas F− removal was mainly influenced by interaction with oxygen functional groups and electrostatic interaction. This study recommends that the bone char pyrolysis temperature used for As and F− removal are 900 °C and 650 °C, respectively. © 2020 Elsevier LtdThis research was performed as a part of PhD research which was supported in part by the Iraqi Government and the Australian Research Training Program
Improving the quality of waste-derived char by removing ash
No full textThis study characterized and removed ash from waste-derived char to improve the quality of char as fuel. Municipal solid waste (MSW) and automobile shredder residue (ASR) were carbonized at 450 ℃ and at 500 ℃ respectively in a rotary kiln with a nitrogen atmosphere for 1 h. MSW and ASR char were subjected to sieving and pulverization-sieving to screen incombustibles and the ash-rich fraction, after which float–sink separation, froth floatation, and oil agglomeration were applied to remove ash from the char. The established target quality was less than 30% ash content and more than 20000 kJ/kg heating value. However, the rate of combustibles recovery had to be lowered to produce a good quality of char along with a high heating value. MSW char attained the targeted quality level using froth floatation or oil agglomeration whereas neither separation method was able to make ASR-derived char satisfy the target. Based on the assumption that particle properties of char are determined by the weight ratio of combustibles and ash, the densities of combustibles and ash in char were estimated using the results of float–sink separation, X-ray diffraction (XRD) analysis, and elemental content. To verify the above assumption, an energy dispersive X-ray/scanning electron microscope (EDX/SEM) analyzer was used to observe char particles
Adsorption of H2S on Residual Biomass Gasification Char
No full textChar is the solid by-product of biomass gasification. Plant owners usually dispose of it at a cost, but its high carbon content and surface area could make it suitable for further applications. In this work, we studied its potential to adsorb hydrogen sulphide (H2S), a common pollutant, e.g. present in the producer gas of gasification, as well as in biogas from anaerobic digestion. We tested different samples of char collected from commercial gasification plants in South Tyrol (Italy). The adsorption was reproduced in a lab-scale fixed bed reactor. The results highlights that all samples could capture hydrogen sulphide, showing different adsorption performance. The surface area of the char and the ash amount seem to affect the removal capacity, although other properties of the materials are probably important. The inlet concentration of hydrogen sulphide does not influence the adsorption capacity significantly
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