193,450 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
Valorisation of lignin – Achievements of the LignoValue project
No full textLignocellulosic biorefinery for production of biofuels, materials and chemicals requires valorization of all fractions including lignin. As a consequence of its poly-aromatic structure, lignin potentially serves as a source for aromatic chemicals. The developed biorefinery concept of the LignoValue project comprises two major steps: (1) Organosolv fractionation of wheat straw and willow into (hemi)cellulose and high purity lignin. (2) Further conversion of the isolated lignin via catalytic pyrolysis, supercritical depolymerization and partial hydrodeoxygenation (HDO) into different components like low molecular phenolic compounds, wood adhesives and fuel additives. The cellulose fraction resulting after organosolv fractionation is effectively hydrolysed by enzymes for biofuel production. Quality assessment of the liberated lignins shows interesting characteristics for follow-up chemistry such as high purity, relatively low molar mass and polydispersity. Catalytic pyrolysis in a fluidised bed at 400-500°C was found to convert organosolv lignin in 35-55% phenolic oil, 10% identified monomeric phenolic compounds, 10-20% water, 5-20% gas and 35-55% char. Supercritical depolymerisation of lignin in carbon dioxide based solvents resulted in a similar spectrum of products, however, at a lower temperature (ca 300°C) but at higher pressures. In both thermochemical processes the use of promotors or catalysts lead to an improved yield of the target monomeric aromatic products. Also the residual char fraction shows interesting properties for use in bio-char applications. Catalytic semi-continuous HDO of lignin in hydrogen atmosphere can be manipulated to yield both light oils or heavy oils as potential additives to fuels. Suitable catalysts were found to convert depolymerised lignin to phenolic oils in high yields. In this process no char formation is observed. The lignin oils were successfully tested on lab scale as partial substitution of phenol in resins for gluing wood panels. The LignoValue concept is critically reviewed in a techno-economic analysis demonstrating the potential for further commercial development and adoptation of this innovative biorefinery process in Europe
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
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
L'amante (poème inédit)
No full textChar René. L'amante (poème inédit). In: Cahiers du monde hispanique et luso-brésilien, n°49, 1987. René Char. p. 4
Lettre à Georges Baudot
No full textChar René. Lettre à Georges Baudot. In: Cahiers du monde hispanique et luso-brésilien, n°49, 1987. René Char. p. 21
Chemically enhanced char for syngas filtering purposes
No full textThis paper investigates the performance of gasification char as syngas filter medium. Char obtained from a small-scale downdraft gasifier was analyzed and chemically enhanced through an acid treatment using a sulfuric acid solution in a thermostatic bath at 40 °C. The treated char presents a higher BET value of 465.9557 m2/g in comparison with the untreated sample which has a BET value of 394.4430 m2/g. However, the treated sample has a low metallic cations content (K, Fe and Sr) and consequentially a low ash content compared to the untreated sampled. Char samples are used as cartridge filter media in order to assess their tar adsorption potential using a modified “Tar Sampling Protocol” method. Experimental results show a noticeable tar content reduction in the syngas using char as filter, in fact the treated char reduces the tar number from 1456 mg/Nm3 to 267.2 mg/Nm3 and the untreated char reduces the tar number from 1456 mg/Nm3 to 179.6 mg/Nm3. The difference in the tar adsorption is probably given by the char ash content that it is less in the treated sample
Charisiana I (Char. Gramm. P. 102.25-P. 103.4 Barwick)
No full textEn este artículo se intenta ofrecer un texto mejorado de Char. Gramm. p. 102.25-p. 103.4 Barwick, lo cual lleva a una revisión de su significado que pone de relieve las diferencias con Gell. 10.24, un texto paralelo usado por H. Keil para hacer conjeturas y enmiendas innecesarias, aceptadas en la edición para Teubner de K. Barwick.In this article, there is an attempt to offer an improved version of the text Char. Gramm. p. 102.25-p. 103.4 Barwick, which leads to a correction of its meaning, that emphasises the differences between this text and Gell. 10.24, a similar text used by H. Kei in order to make speculations and unnecessary corrections, accepted in the edition by K. Barwick for Teubner
Phosphorus availability from bone char in a P-fixing soil influenced by root-mycorrhizae-biochar interactions
No full textThe objectives of this study were to evaluate (1)
the fertilizer potential of bone char, (2) the effects of
wood biochar on plant-available phosphorus (P), and (3)
the role of root-mycorrhizae-biochar interactions in
plant P acquisition from a P-fixing soil.
Methods Incubation and pot experiments were conducted with a P-fixing soil and maize with or without root
hairs and arbuscular mycorrhizae (AM) inoculation.
Olsen-, resin-P and plant P accumulation were used to
estimate P availability from bone char, co-pyrolyzed
bone char-wood biochar, and separate bone char and
wood biochar additions produced at 60, 350 and 750 °C,
and Triple Superphosphate (TSP).
Results Maize inoculated with AM showed similar P
accumulation when fertilized with either 750 °C bone
char or TSP. Pyrolyzing bone did not increase extractable P in soil in comparison to unpyrolyzed bone, apart
from a 67 % increase in resin-extractable P after additions of bone char pyrolyzed at 350 °C. Despite greater
Olsen-P extractability, co-pyrolysis of bone with wood
reduced maize P uptake. Wood biochars reduced resin-P
from bone char by 14–26 %, whereas oven-dried wood
increased resin-P by 23 %.
Conclusions Bone char is an effective P fertilizer, especially if root-AM interactions are simultaneously considered. Biochar influences plant access to soil P and
requires careful management to improve P availability
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