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Gasification
Kinds of Gasification Terms modified by Gasification Selected AbstractsControlled Etching of Carbon Nanotubes by Iron-Catalyzed Steam Gasification,ADVANCED MATERIALS, Issue 21 2007W. Xia A localized etching method based on catalytic steam gasification was developed to modify carbon nanotubes in a pre-determined manner. The etching, occurring only at the interface, created different etching patterns depending on the iron catalyst by means of an eco-friendly, low-cost process using water vapor. Both the surface roughness and the number of surface defects such as edge planes were significantly enhanced. [source] Potential of biomass-fired combined heat and power plants considering the spatial distribution of biomass supply and heat demandINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2010Johannes Schmidt Abstract Combined heat and power (CHP) plants fired by forest wood can significantly contribute to attaining the target of increasing the share of renewable energy production. However, the spatial distribution of biomass supply and of heat demand limits the potentials of CHP production. This article assesses CHP potentials using a mixed integer programming model that optimizes locations of bioenergy plants. Investment costs of district heating infrastructure are modeled as a function of heat demand densities, which can differ substantially. Gasification of biomass in a combined cycle process is assumed as production technology. Some model parameters have a broad range according to a literature review. Monte-Carlo simulations have therefore been performed to account for model parameter uncertainty in our analysis. The model is applied to assess CHP potentials in Austria. Optimal locations of plants are clustered around big cities in the east of the country. At current power prices, biomass-based CHP production allows producing around 3% of the total energy demand in Austria. Yet, the heat utilization decreases when CHP production increases due to limited heat demand that is suitable for district heating. Production potentials are most sensitive to biomass costs and power prices. Copyright © 2009 John Wiley & Sons, Ltd. [source] Gasification of char particles in packed beds: analysis and resultsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2001S. Dasappa Abstract In this paper a packed bed of char particles is considered for experimental study and analysis. The packed char bed is modelled by extending the single-particle analysis (Dasappa et al., 1994a, Chem. Eng. Sci.49,2:223,232. Dasappa et al., 1994b, Twenty-fifth Symposium (International) on Combustion, pp. 1619,1628. Dasappa et al., 1998, Twenty-seventh Symposium (International) on Combustion, pp. 1335,1342.). All the reactions related to gasification are introduced into the reaction system as in Dasappa et al. (1998). The propagation of the reaction front into the packed char bed against the air stream is modelled. The results are compared with the experimental data on a model quartz reactor using charcoal. Experimental data of propagation of the reaction front through the packed bed from the present study and of Groeneveld's charcoal gasifier are used for comparison. Using the analysis of Dosanjh et al. 1987 (Combust. Flame68:131,142), it is shown that heat loss dominates the heat generation at the quench condition. It is also shown that increasing the oxygen fraction in air has resulted in flame front to propagate into the char bed. The critical air mass flux for peak propagation rate in a bed of char is found to be 0.1 kg m,2 s. Copyright © 2001 John Wiley & Sons, Ltd. [source] Kinetic model for noncatalytic supercritical water gasification of cellulose and ligninAICHE JOURNAL, Issue 9 2010Fernando L. P. Resende Abstract This article reports the first kinetics model for Supercritical Water Gasification (SCWG) that describes the formation and interconversion of individual gaseous species. The model comprises 11 reactions, and it uses a lumping scheme to handle the large number of intermediate compounds. We determined numerical values for the rate constants in the model by fitting it to experimental data previously reported for SCWG of cellulose and lignin. We validated the model by showing that it accurately predicts gas yields at biomass loadings and water densities not used in the parameter estimation. Sensitivity analysis and reaction rate analysis indicate that steam-reforming and water,gas shift are the main sources of H2 in SCWG, and intermediate species are the main sources of CO, CO2, and CH4. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Enhancing high water content biomass gasification with impregnated Ca in fuel dryingAICHE JOURNAL, Issue 10 2006Guangwen Xu Abstract In view of energy conversion efficiency, the gas production from high water content (>60 wt.%) biomass via gasification is necessarily conducted with fuel drying in advance. In regard to this kind of processes, the present study was devised to impregnate Ca onto fuel during fuel drying and thereby to increase fuel's gasification reactivity to raise the gas production efficiency with minimal additional cost. By employing wet coffee grounds as a model biomass fuel and slurry dewatering in kerosene as the adopted drying technology, the Ca impregnation was implemented through dosing Ca(OH)2 into a fuel-kerosene slurry and in turn treating the slurry in the same way as for the case without Ca addition. The resulting Ca (4.0 wt.% load in CaO base) exhibited high dispersion through the fuel matrix in both SEM-EDX image and XRD spectrum. Gasification of the fuel in a pilot dual fluidized gasification setup further demonstrated that the fuel possessed distinctively high reaction reactivity. This led it to show C and H conversions of 91% and 138%, respectively, at a reaction temperature of about 1083 K, whereas these conversions were only 70% and 92% for the fuel with a similar amount of physically mixed CaO. The catalytic effect of the impregnated Ca manifested also on hydrocarbon reforming and water gas shift, making the resulting product gas evidently rich in H2 and lean in CO and hydrocarbons. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Thermal modeling and simulation of an integrated solid oxide fuel cell and charcoal gasification systemENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2009C. Ozgur Colpan Abstract In this study we propose a novel integrated charcoal gasification and solid oxide fuel cell (SOFC) system, which is intended to produce electricity and heat simultaneously. This system mainly consists of an updraft gasifier using air and steam as the gasification agents, a planar and direct internal reforming SOFC and a low temperature gas cleanup system. The performance of this system is assessed through numerical modeling using a pre-developed and validated heat transfer model of the SOFC and thermodynamic models for the rest of the components. These models are used to simulate the performance of the cell and system for a case study. In addition, a parametric study is conducted to assess the effect of Reynolds number at the fuel channel inlet of the SOFC on the cell performance, e.g., fuel utilization and power density, and the system performance, e.g., electrical efficiency, exergetic efficiency, and power to heat ratio. The number of stacks is also calculated for different Reynolds numbers to discuss the economical feasibility of the integrated system. The results show that the electrical efficiency, exergetic efficiency and power to heat ratio of this system are 33.31%, 45.72%, and 1.004, respectively, for the base case. The parametric study points out that taking the Reynolds number low yields higher electrical and exergetic efficiencies for the system, but it also increases the cost of the system. © 2009 American Institute of Chemical Engineers Environ Prog, 2009 [source] Characterization of biochar from fast pyrolysis and gasification systemsENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2009Catherine E. Brewer Abstract Thermochemical processing of biomass produces a solid product containing char (mostly carbon) and ash. This char can be combusted for heat and power, gasified, activated for adsorption applications, or applied to soils as a soil amendment and carbon sequestration agent. The most advantageous use of a given char depends on its physical and chemical characteristics, although the relationship of char properties to these applications is not well understood. Chars from fast pyrolysis and gasification of switchgrass and corn stover were characterized by proximate analysis, CHNS elemental analysis, Brunauer-Emmet-Teller (BET) surface area, particle density, higher heating value (HHV), scanning electron microscopy, X-ray fluorescence ash content analysis, Fourier transform infrared spectroscopy using a photo-acoustic detector (FTIR-PAS), and quantitative 13C nuclear magnetic resonance spectroscopy (NMR) using direct polarization and magic angle spinning. Chars from the same feedstocks produced under slow pyrolysis conditions, and a commercial hardwood charcoal, were also characterized. Switchgrass and corn stover chars were found to have high ash content (32,55 wt %), much of which was silica. BET surface areas were low (7,50 m2/g) and HHVs ranged from 13 to 21 kJ/kg. The aromaticities from NMR, ranging between 81 and 94%, appeared to increase with reaction time. A pronounced decrease in aromatic CH functionality between slow pyrolysis and gasification chars was observed in NMR and FTIR-PAS spectra. NMR estimates of fused aromatic ring cluster size showed fast and slow pyrolysis chars to be similar (,7,8 rings per cluster), while higher-temperature gasification char was much more condensed (,17 rings per cluster). © 2009 American Institute of Chemical Engineers Environ Prog, 2009 [source] Apportionment of polycyclic aromatic hydrocarbon sources in lower Fox River, USA, sediments by a chemical mass balance modelENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2000Ming-Chien Su Abstract Four sediment cores were collected from the lower Fox River, Wisconsin, USA, to identify possible sources of polycyclic aromatic hydrocarbons (PAHs) using a chemical mass balance model. The cores, which were obtained in 1995 from areas close to Green Bay, Wisconsin, USA, had total PAH concentrations between 19.3 and 0.34 ppm. To determine historical trends of PAH inputs, 210Pb and 137Cs dating was used, and elemental carbon particle analysis was done to characterize particles from the combustion of coal, wood, and petroleum. Source fingerprints were taken from the literature. Our results indicate that coke oven emissions, highway dust, coal gasification, and wood burning are likely sources of PAHs in the lower Fox River. Coke oven emissions are in the range of 40 to 90% of total PAHs, and this fraction decreases from 1930 to 1990, except in core Fox River,A (FR-A). The overall highway dust (HWY) contribution is between 10 and 75%, and this fraction increases from 1930 to present, except in core FR-A. The wood burning (WB) contribution (i.e., wood burning or coal gasification) is less than 7% in cores FR-B, FR-C, and FR-D. In core FR-A, a maximum (,23%) is found around 1960. The contribution of wood burning has changed from less than 6% in 1950 to between 3 and 10% in 1995. Evidence of aerobic biodegradation or photolysis in the sediment of phenanthrene, with a half-life of approximately 0.5 years has been found at the site of core FR-D, which is the shallowest (1.1 m) of the four core sites. [source] The Contribution of Bioenergy to a New Energy ParadigmEUROCHOICES, Issue 3 2005Daniel De La Torre Ugarte Biomass is a widely available resource that is receiving increased consideration as a renewable substitute for fossil fuels. Developed sustainably and used efficiently, it can induce growth in developing countries, reduce oil demand, and address environmental problems. The potential benefits include: reduction of greenhouse gases, recuperation of soil productivity and degraded land, economic benefits from adding value to agricultural activities and improving access to and quality of energy services. The production of bioenergy involves a range of technologies, including solid combustion, gasification, and fermentation. These technologies produce energy from a diverse set of biological resources - traditional crops, crop residues, energy-dedicated crops, dung, and the organic component of urban waste. The results are bioenergy products that provide multiple energy services: cooking fuel, heat, electricity and transportation fuels. It is this very diversity that holds the potential of a win-win-win for the environment, social and economic development. Bioenergy has to be viewed not as a replacement for oil, but as an element of a portfolio of renewable sources of energy. Coherent and mutually supportive environmental and economic policies may be needed to encourage the emergence of a globally dispersed bioenergy industry that will pursue a path of sustainable development. La biomasse est une resource largement répandue, qui commence à retenir l'attention comme substitut renouvelable aux énergies fossiles. En l'utilisant de façon efficace et durable, on peut accélérer la croissance des pays en voie de développement, réduire la demandepour le pétrole et résoudre certains problèmes d'environnement. Au nombre des bénéfices potentiels il faut mettre : la réduction des émissions de gaz à effet de serre, la reconstitution de la fertilité dessols et des terres dégradées, les avantages économiques liés à l'accroissement de la production agricole et à l'amélioration des services énergétiques, tant en qualité qu'en accessibilité. La production de bioénergie met en oeuvre un large éventail de techniques parmi lesquelles la combustionde produits solides, la gazéification et la fermentation. Elles produisent de l'énergie à partir d'une grande variété de sources biologiques : cultures traditionnelles, résidus de cultures, cultures spécialisées, fumiers et déchets organiques urbains. Les produits bio-énergétiques qui en résultent couvrent une grande variété d'usages : énergie de cuisson, chauffage, électricité et transports. C'est précisément sur cette diversité que repose l'espoir de gains dans toutes les directions, sociales, environnementales et économiques. Il ne faut pas voir la bioénergie comme un simple substitut au pétrole, mais comme un portefeuille de ressources renouvelables. Pour encourager l'émergence d'une industrie bioénergétique largement répandue et susceptible de contribuer au développement durable, il faudra sans doute élaborer des politiques économiques et environnementales cohérentes, capables de se soutenir mutuellement. Bei Biomasse handelt es sich umeine weithin verfügbare Ressource, welche zunehmend als erneuerbarer Ersatz für fossile Brennstoffe in Betracht gezogen wird. Sie kann bei nachhaltiger Entwicklung und effizienter Nutzung zu Wachstum in den Entwicklungsländern führen, die Nachfrage nach Öl senken und dazu beitragen, die Umweltprobleme in den Griff zu bekommen. Zu den potenziellen Nutzen gehÖren: Verringerung der Treibhausgase, Wiederherstellung von Bodenproduktivität sowie von erodiertem Land, wirtschaftlicher Nutzen durch zusätzliche Wertschöpfung aus landwirtschaftlicher Aktivität und besserer Zugang zu und Qualität in der Energieversorgung. Bei der Erzeugungvon Bioenergie kommen eine Reihe von verschiedenen Technologien zur Anwendung, z.B. Verbrennung fester Brennstoffe, Vergasung sowie Gärung. Diese Technologien erzeugen Energie mittels unterschiedlicher biologischer Ressourcen , traditionelle Feldfrüchte und deren Rückstände, spezielle Energiepflanzen, Mist sowie der organische Anteil städtischer Abfälle. Die daraus erzeugte Bioenergie kann zum Kochen, zum Heizen, als Elektrizität oder als Treibstoff genutzt werden. Gerade in dieser Vielfalt liegt der potenzielle Gewinn für die Umwelt und die soziale sowie die wirtschaftliche Entwicklung. Bioenergie sollte nicht als ein Ersatz für Öl, sondern als Bestandteil des Portfolios erneuerbarer Energiequellen angesehen werden. Kohärente und sich gegenseitig unterstützende ökologische und Ökonomische Politikmaßnahmen könntenerforderlich sein, um die Entstehung einer global verbreiteten Bioenergieindustrie zu begünstigen, welche eine nachhaltige Entwicklung verfolgt. [source] Inherent flammability parameters,Room corner test applicationFIRE AND MATERIALS, Issue 8 2009J. G. Quintiere Abstract It has been hypothesized that four parameters are solely responsible for a material's performance in a flammability scenario. This excludes effects of material physical integrity, i.e. melting, delamination, etc. They are (1) the critical heat flux below which piloted ignition cannot occur (CHF), (2) the ratio of heat of combustion to heat of gasification (HRP), (3) the thermal response parameter related to the thermal inertia and the ignition temperature (TRP), and (4) the available energy per unit area (AEP). The fire scenario controls the process by its initial heat flux and region of ignition. The hypothesis is applied to 54 tests of the ISO Room Corner Test to assess its validity. It is shown that these four parameters give good correlations in predicting the time to flashover and whether it occurs. In principle, different correlations could be developed for other scenarios of tests and fire configurations. Copyright © 2009 John Wiley & Sons, Ltd. [source] Controlled Etching of Carbon Nanotubes by Iron-Catalyzed Steam Gasification,ADVANCED MATERIALS, Issue 21 2007W. Xia A localized etching method based on catalytic steam gasification was developed to modify carbon nanotubes in a pre-determined manner. The etching, occurring only at the interface, created different etching patterns depending on the iron catalyst by means of an eco-friendly, low-cost process using water vapor. Both the surface roughness and the number of surface defects such as edge planes were significantly enhanced. [source] Implications of system expansion for the assessment of well-to-wheel CO2 emissions from biomass-based transportationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2010Elisabeth Wetterlund Abstract In this paper we show the effects of expanding the system when evaluating well-to-wheel (WTW) CO2 emissions for biomass-based transportation, to include the systems surrounding the biomass conversion system. Four different cases are considered: DME via black liquor gasification (BLG), methanol via gasification of solid biomass, lignocellulosic ethanol and electricity from a biomass integrated gasification combined cycle (BIGCC) used in a battery-powered electric vehicle (BPEV). All four cases are considered with as well as without carbon capture and storage (CCS). System expansion is used consistently for all flows. The results are compared with results from a conventional WTW study that only uses system expansion for certain co-product flows. It is shown that when expanding the system, biomass-based transportation does not necessarily contribute to decreased CO2 emissions and the results from this study in general indicate considerably lower CO2 mitigation potential than do the results from the conventional study used for comparison. It is shown that of particular importance are assumptions regarding future biomass use, as by expanding the system, future competition for biomass feedstock can be taken into account by assuming an alternative biomass usage. Assumptions regarding other surrounding systems, such as the transportation and the electricity systems are also shown to be of significance. Of the four studied cases without CCS, BIGCC with the electricity used in a BPEV is the only case that consistently shows a potential for CO2 reduction when alternative use of biomass is considered. Inclusion of CCS is not a guarantee for achieving CO2 reduction, and in general the system effects are equivalent or larger than the effects of CCS. DME from BLG generally shows the highest CO2 emission reduction potential for the biofuel cases. However, neither of these options for biomass-based transportation can alone meet the needs of the transport sector. Therefore, a broader palette of solutions, including different production routes, different fuels and possibly also CCS, will be needed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effect of supplementary firing options on cycle performance and CO2 emissions of an IGCC power generation systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2009N. V. Gnanapragasam Abstract Supplementary firing is adopted in combined-cycle power plants to reheat low-temperature gas turbine exhaust before entering into the heat recovery steam generator. In an effort to identify suitable supplementary firing options in an integrated gasification combined-cycle (IGCC) power plant configuration, so as to use coal effectively, the performance is compared for three different supplementary firing options. The comparison identifies the better of the supplementary firing options based on higher efficiency and work output per unit mass of coal and lower CO2 emissions. The three supplementary firing options with the corresponding fuel used for the supplementary firing are: (i) partial gasification with char, (ii) full gasification with coal and (iii) full gasification with syngas. The performance of the IGCC system with these three options is compared with an option of the IGCC system without supplementary firing. Each supplementary firing option also involves pre-heating of the air entering the gas turbine combustion chamber in the gas cycle and reheating of the low-pressure steam in the steam cycle. The effects on coal consumption and CO2 emissions are analysed by varying the operating conditions such as pressure ratio, gas turbine inlet temperature, air pre-heat and supplementary firing temperature. The results indicate that more work output is produced per unit mass of coal when there is no supplementary firing. Among the supplementary firing options, the full gasification with syngas option produces the highest work output per unit mass of coal, and the partial gasification with char option emits the lowest amount of CO2 per unit mass of coal. Based on the analysis, the most advantageous option for low specific coal consumption and CO2 emissions is the supplementary firing case having full gasification with syngas as the fuel. Copyright © 2008 John Wiley & Sons, Ltd. [source] Exergetic efficiency and options for improving sewage sludge gasification in supercritical waterINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2007Edgar Gasafi Abstract The present article deals with an exergy analysis of a process under development for the gasification of biomass in supercritical water (supercritical water gasification, SCWG). This process is aimed at generating hydrogen out of the biogenic feedstock sewage sludge. The principle of the process is based on making use of the modifications of specific physical and chemical properties of water above the critical point (T=374°C, p=221 bar). These properties allow for a nearly complete conversion of the organic substance contained in the feed material into energy-rich fuel gases, containing hydrogen, carbon dioxide and methane. Based on a steady-state model of the process, exergy flow rates are calculated for all components and a detailed exergy analysis is performed. From the exergetic variables, options to improve the individual plant components as well as the overall plant are derived. The components with the highest proportion of exergy destruction in the complete process are identified and possibilities of improving them and the complete system in order to increase the overall efficiency are demonstrated. The combustion chamber necessary for heat supply is found to be the component with the highest proportion of exergy destruction of the complete plant. Moreover, the components of air preheater, reactor contribute significantly to the exergy destruction of the complete system. Copyright © 2006 John Wiley & Sons, Ltd. [source] Recovery of CO2 with MEA and K2CO3 absorption in the IGCC systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2004Baoqun Wang Abstract Recovery of CO2 with monoethanolamine (MEA) and hot potassium carbonate (K2CO3) absorption processes in an integrated gasification combined cycle (IGCC) power plant was studied for the purpose of development of greenhouse gas control technology. Based on energy and exergy analysis of the two systems, improvement options were provided to further reduce energy penalty for the CO2 separation in the IGCC system. In the improvement options, the energy consumption for CO2 separation is reduced by about 32%. As a result, the thermal efficiency of IGCC system is increased by 2.15 percentage-point for the IGCC system with MEA absorption, and by 1.56 percentage-point for the IGCC system with K2CO3 absorption. Copyright © 2004 John Wiley & Sons, Ltd. [source] Performance study of a partial gasification pressurized combustion topping gas cycle and split rankine combined cycle: Part II,Exergy analysisINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2003S. De Abstract In addition to the energy analysis in part I of this paper, an exergy analysis of an advanced combined cycle is presented in this part of the paper to identify the major causes of thermodynamic imperfections. The exergy loss and exergetical efficiency of each of the components of the plant are investigated for variations of design and operating parameters. This is done to explore the possible improvements in the second law performance of this plant. Copyright © 2003 John Wiley & Sons, Ltd. [source] Fundamental study on biomass-fuelled ceramic fuel cellINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2002B. Zhu Abstract Recent development in the advanced intermediate temperature (400 to 700°C) ceramic fuel cell (CFC) research brings up feasibility and new opportunity to develop innovative biomass-fuelled CFC technology. This work focuses on fundamentals of the biomass-fuelled CFCs based on available biofuel resources through thermochemical conversion technologies. Both real producer gas from biomass gasification and imitative compounded gas were used as the fuel to operate the CFCs in the biomass CFC testing station. The composition of the fuel gas was varied in a wide range of practices of the present conversion technology both in KTH and Shandong Institute of Technology (SDIT). CFC performances were achieved between 100 and 700 mW cm,2 at 600,800°C corresponding to various gas compositions. A high performance close to 400 mW cm,2 was obtained at 600°C for the gas with the composition of H2 (50 per cent)+CO (15 per cent)+CO2 (15 per cent)+N2 (20 per cent) and more than 600 mW cm,2 for the H2 (55 per cent)+CO (28 per cent)+CO2 (17 per cent) at 700°C. This paper presents the experimental results and discusses the fundamentals and future potentiality on the biomass fuelled CFCs. Copyright © 2002 John Wiley & Sons, Ltd. [source] Gasification of char particles in packed beds: analysis and resultsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2001S. Dasappa Abstract In this paper a packed bed of char particles is considered for experimental study and analysis. The packed char bed is modelled by extending the single-particle analysis (Dasappa et al., 1994a, Chem. Eng. Sci.49,2:223,232. Dasappa et al., 1994b, Twenty-fifth Symposium (International) on Combustion, pp. 1619,1628. Dasappa et al., 1998, Twenty-seventh Symposium (International) on Combustion, pp. 1335,1342.). All the reactions related to gasification are introduced into the reaction system as in Dasappa et al. (1998). The propagation of the reaction front into the packed char bed against the air stream is modelled. The results are compared with the experimental data on a model quartz reactor using charcoal. Experimental data of propagation of the reaction front through the packed bed from the present study and of Groeneveld's charcoal gasifier are used for comparison. Using the analysis of Dosanjh et al. 1987 (Combust. Flame68:131,142), it is shown that heat loss dominates the heat generation at the quench condition. It is also shown that increasing the oxygen fraction in air has resulted in flame front to propagate into the char bed. The critical air mass flux for peak propagation rate in a bed of char is found to be 0.1 kg m,2 s. Copyright © 2001 John Wiley & Sons, Ltd. [source] Corn and rice waste: a comparative and critical presentation of methods and current and potential uses of treated wasteINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2008Ioannis S. Arvanitoyannis Summary Although corn and rice waste can be hardly classified among the most hazardous waste, their treatment is very important in view of the great volume of waste materials involved. In this review article, an update is provided for most of the waste treatment techniques (composting, pyrolysis, gasification, combustion) used to alter the physical, chemical or biological character of the waste, to reduce its volume and/or toxicity and to make the waste safer for disposal. Furthermore, all current and potential uses of treated corn and rice waste such as fertilisers, biomass and biogas/biofuel are summarised. Four comprehensive tables and six figures provide a thorough presentation of both waste treatment methods (characteristics, advantages and disadvantages) and uses of treated corn and rice waste. [source] Microporous activated carbon spheres prepared from resole-type crosslinked phenolic beads by physical activationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Arjun Singh Abstract Microporous activated carbon spheres (ACSs) with a high specific Brunauer,Emmet,Teller (BET) surface area were prepared from resole-type spherical crosslinked phenolic beads (PBs) by physical activation. The PBs used as precursors were synthesized in our laboratory through the mixing of phenol and formaldehyde in the presence of an alkaline medium by suspension polymerization. The effects of the gasification time, temperature, and flow rate of the gasifying agent on the surface properties of ACSs were investigated. ACSs with a controllable pore structure derived from carbonized PBs were prepared by CO2 gasification. Surface properties of ACSs, such as the BET surface area, pore volume, pore size distribution, and pore diameters, were characterized with BET and Dubinin,Reduchkevich equations based on N2 adsorption isotherms at 77 K. The results showed that ACSs with a 32,88% extent of burn-off with CO2 gasification exhibited a BET surface area ranging from 574 to 3101 m2/g, with the pore volume significantly increased from 0.29 to 2.08 cm3/g. The pore size and its distribution could be tailored by the selection of suitable conditions, including the gasification time, temperature, and flow rate of the gasifying agents. The experimental results of this analysis revealed that ACSs obtained under different conditions were mainly microporous. The development of the surface morphology of ACSs was also studied with scanning electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Supercritical water for environmental technologiesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2010Dr Anne Loppinet-Serani Abstract OVERVIEW: Supercritical water is a great medium in which to perform chemical reactions and to develop processes. Due to its unique thermo-physico-chemical properties, supercritical water is able to play the role of solvent of organic compounds and/or to react with them. These specific properties have been used since the 1990s to develop new technologies dedicated to the environment and energy. IMPACT: Supercritical water based technologies are innovative and efficient processes having a strong impact on society, the environment and the economy, and is termed a sustainable technology. APPLICATIONS: Three main applications for supercritical water technology are under development: (i) supercritical water oxidation (SCWO); (ii) supercritical water biomass gasification (SCBG); and (iii) hydrolysis of polymers in supercritical water (HPSCW) for composites/plastics recycling. In this paper some fundamentals of supercritical water are first presented to introduce the above three major developments. Then these technologies are reviewed in terms of their present and future industrial development and their impact on the environment and on energy production. Copyright © 2010 Society of Chemical Industry [source] Kinetic model for noncatalytic supercritical water gasification of cellulose and ligninAICHE JOURNAL, Issue 9 2010Fernando L. P. Resende Abstract This article reports the first kinetics model for Supercritical Water Gasification (SCWG) that describes the formation and interconversion of individual gaseous species. The model comprises 11 reactions, and it uses a lumping scheme to handle the large number of intermediate compounds. We determined numerical values for the rate constants in the model by fitting it to experimental data previously reported for SCWG of cellulose and lignin. We validated the model by showing that it accurately predicts gas yields at biomass loadings and water densities not used in the parameter estimation. Sensitivity analysis and reaction rate analysis indicate that steam-reforming and water,gas shift are the main sources of H2 in SCWG, and intermediate species are the main sources of CO, CO2, and CH4. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Evaporation of pyrolysis oil: Product distribution and residue char analysisAICHE JOURNAL, Issue 8 2010Guus van Rossum Abstract The evaporation of pyrolysis oil was studied at varying heating rates (,1,106°C/min) with surrounding temperatures up to 850°C. A total product distribution (gas, vapor, and char) was measured using two atomizers with different droplet sizes. It was shown that with very high heating rates (,106°C/min) the amount of char was significantly lowered (,8%, carbon basis) compared to the maximum amount, which was produced at low heating rates using a TGA (,30%, carbon basis; heating rate 1°C/min). The char formation takes place in the 100,350°C liquid temperature range due to polymerization reactions of compounds in the pyrolysis oil. All pyrolysis oil fractions (whole oil, pyrolytic lignin, glucose and aqueous rich/lean phase) showed charring behavior. The pyrolysis oil chars age when subjected to elevated temperatures (,700°C), show similar reactivity toward combustion and steam gasification compared with chars produced during fast pyrolysis of solid biomass. However, the structure is totally different where the pyrolysis oil char is very light and fluffy. To use the produced char in conversion processes (energy or syngas production), it will have to be anchored to a carrier. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Chemical-looping combustion process: Kinetics and mathematical modelingAICHE JOURNAL, Issue 4 2010Ion Iliuta Abstract Chemical Looping Combustion technology involves circulating a metal oxide between a fuel zone where methane reacts under anaerobic conditions to produce a concentrated stream of CO2 and water and an oxygen rich environment where the metal is reoxidized. Although the needs for electrical power generation drive the process to high temperatures, lower temperatures (600,800°C) are sufficient for industrial processes such as refineries. In this paper, we investigate the transient kinetics of NiO carriers in the temperature range of 600 to 900°C in both a fixed bed microreactor (WHSV = 2-4 g CH4/h/g oxygen carrier) and a fluid bed reactor (WHSV = 0.014-0.14 g CH4/h per g oxygen carrier). Complete methane conversion is achieved in the fluid bed for several minutes. In the microreactor, the methane conversion reaches a maximum after an initial induction period of less than 10 s. Both CO2 and H2O yields are highest during this induction period. As the oxygen is consumed, methane conversion drops and both CO and H2 yields increase, whereas the CO2 and H2O concentrations decrease. The kinetics parameter of the gas,solids reactions (reduction of NiO with CH4, H2, and CO) together with catalytic reactions (methane reforming, methanation, shift, and gasification) were estimated using experimental data obtained on the fixed bed microreactor. Then, the kinetic expressions were combined with a detailed hydrodynamic model to successfully simulate the comportment of the fluidized bed reactor. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Optimization of energy usage for fleet-wide power generating system under carbon mitigation optionsAICHE JOURNAL, Issue 12 2009A. Elkamel Abstract This article presents a fleet-wide model for energy planning that can be used to determine the optimal structure necessary to meet a given CO2 reduction target while maintaining or enhancing power to the grid. The model incorporates power generation as well as CO2 emissions from a fleet of generating stations (hydroelectric, fossil fuel, nuclear, and wind). The model is formulated as a mixed integer program and is used to optimize an existing fleet as well as recommend new additional generating stations, carbon capture and storage, and retrofit actions to meet a CO2 reduction target and electricity demand at a minimum overall cost. The model was applied to the energy supply system operated by Ontario power generation (OPG) for the province of Ontario, Canada. In 2002, OPG operated 79 electricity generating stations; 5 are fueled with coal (with a total of 23 boilers), 1 by natural gas (4 boilers), 3 nuclear, 69 hydroelectric and 1 wind turbine generating a total of 115.8 TWh. No CO2 capture process existed at any OPG power plant; about 36.7 million tonnes of CO2 was emitted in 2002, mainly from fossil fuel power plants. Four electricity demand scenarios were considered over a span of 10 years and for each case the size of new power generation capacity with and without capture was obtained. Six supplemental electricity generating technologies have been allowed for: subcritical pulverized coal-fired (PC), PC with carbon capture (PC+CCS), integrated gasification combined cycle (IGCC), IGCC with carbon capture (IGCC+CCS), natural gas combined cycle (NGCC), and NGCC with carbon capture (NGCC+CCS). The optimization results showed that fuel balancing alone can contribute to the reduction of CO2 emissions by only 3% and a slight, 1.6%, reduction in the cost of electricity compared to a calculated base case. It was found that a 20% CO2 reduction at current electricity demand could be achieved by implementing fuel balancing and switching 8 out of 23 coal-fired boilers to natural gas. However, as demand increases, more coal-fired boilers needed to be switched to natural gas as well as the building of new NGCC and NGCC+CCS for replacing the aging coal-fired power plants. To achieve a 40% CO2 reduction at 1.0% demand growth rate, four new plants (2 NGCC, 2 NGCC+CCS) as well as carbon capture processes needed to be built. If greater than 60% CO2 reductions are required, NGCC, NGCC+CCS, and IGCC+CCS power plants needed to be put online in addition to carbon capture processes on coal-fired power plants. The volatility of natural gas prices was found to have a significant impact on the optimal CO2 mitigation strategy and on the cost of electricity generation. Increasing the natural gas prices resulted in early aggressive CO2 mitigation strategies especially at higher growth rate demands. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Modeling of CO2 gasification of carbon for integration with solid oxide fuel cellsAICHE JOURNAL, Issue 4 2009Andrew C. Lee Abstract This modeling study focuses on gasification of carbon by CO2 in a minimally fluidized bed containing a solid oxide fuel cell (SOFC). Kinetic parameters for a five-step reaction mechanism characterizing the Boudouard reaction (C + CO2 , 2CO) were determined thermogravimetrically at 1 atm from 973 to 1273 K. Experimentally determined kinetic parameters are employed in a transport model that predicts velocities and gas concentration profiles established in the carbon bed as a consequence of convection, diffusion, and heterogeneous reaction. The model is used to simulate the effect of an imbedded SOFC, in contact with the carbon bed. Although the model does not assume particular I-V characteristics for the fuel cell, it indicates that current densities in the practical range of 100,1000 mA/cm2 can be supported. Results show that temperature strongly affects the current density, whereas CO2 flow rate has only a weak effect. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Elucidation of the interaction among cellulose, xylan, and lignin in steam gasification of woody biomassAICHE JOURNAL, Issue 2 2009Chihiro Fushimi Abstract The reaction mechanism for gas and tar evolution in the steam gasification of cellulose, lignin, xylan, and real biomass (pulverized eucalyptus) was investigated with a continuous cross-flow moving bed type differential reactor, in which tar and gases can be fractionated according to reaction time. In the steam gasification of real biomass, the evolution rates of water-soluble tar (derived from cellulose and hemicelluloses) and water-insoluble tar (derived from lignin) decrease with increasing reaction time. It was found that the evolution of water-soluble tar occurs earlier than in the gasification of pure cellulose, indicating an interaction of the three components. The predicted yield of water-insoluble tar is substantially less than that of real biomass. This implies that the evolution of tar from the lignin component of biomass is enhanced, compared with pure lignin gasification, by other components. The gas evolution rate from real biomass is similar to that predicted by the superposition of cellulose, lignin, and xylan. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] Enhancing high water content biomass gasification with impregnated Ca in fuel dryingAICHE JOURNAL, Issue 10 2006Guangwen Xu Abstract In view of energy conversion efficiency, the gas production from high water content (>60 wt.%) biomass via gasification is necessarily conducted with fuel drying in advance. In regard to this kind of processes, the present study was devised to impregnate Ca onto fuel during fuel drying and thereby to increase fuel's gasification reactivity to raise the gas production efficiency with minimal additional cost. By employing wet coffee grounds as a model biomass fuel and slurry dewatering in kerosene as the adopted drying technology, the Ca impregnation was implemented through dosing Ca(OH)2 into a fuel-kerosene slurry and in turn treating the slurry in the same way as for the case without Ca addition. The resulting Ca (4.0 wt.% load in CaO base) exhibited high dispersion through the fuel matrix in both SEM-EDX image and XRD spectrum. Gasification of the fuel in a pilot dual fluidized gasification setup further demonstrated that the fuel possessed distinctively high reaction reactivity. This led it to show C and H conversions of 91% and 138%, respectively, at a reaction temperature of about 1083 K, whereas these conversions were only 70% and 92% for the fuel with a similar amount of physically mixed CaO. The catalytic effect of the impregnated Ca manifested also on hydrocarbon reforming and water gas shift, making the resulting product gas evidently rich in H2 and lean in CO and hydrocarbons. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Influence of novel cycle concepts on the high-temperature corrosion of power plantsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 5 2008Bettina BordenetArticle first published online: 29 MAY 200 Abstract The aim to reduce CO2 emissions has triggered the evaluation of new cycle concepts for power plants. CO2 -capture concepts are also evaluated to add on new and existing power plants. For combined cycle power plants (CCPP), different cycles are investigated such as integrated gasification (IGCC) or oxy-fuel firing. Besides the difference in combustion compared to a conventional CCPP, the environmental boundary conditions are changed and will affect the oxidation and corrosion life of the materials in the hot-gas path of the gas turbine and the heat-recovery steam generator. For the circulating fluidised bed power plants, the biomass co-firing and the oxy-fuel firing are also foreseen for CO2 -emission reduction. The fireside corrosion of the water walls will be influenced by these concepts and the changed fuel. The corrosion risk has been evaluated for two new power plant concepts: combined cycle with exhaust gas recirculation and pulverised coal-fired boiler with oxy-fuel firing. Based on this evaluation, the consequences for the testing conditions and the material selection have been discussed in detail. [source] Hydrodynamics of gas,solid fluidization in tapered bedsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009J. S. N. Murthy Abstract Gas,solid fluidization has a wide range of industrial applications like catalytic reactions, combustion, gasification, etc. In a number of these applications, there is particle size reduction during the operation leading to severe entrainment and limitation of operating velocity. The various problems associated with particles of different sizes or changing particles sizes could be overcome by adopting tapered beds in fluidization operation. In the present investigation, the fluidization phenomenon in tapered beds has been critically assessed through experimental investigations using particles of different sizes and materials and wide range of apex angles of the vessels. The effect of particle size and apex angle on the fluidization behaviour is clearly brought out which has not been reported so far in literature. The importance of compressive force existing in tapered beds is highlighted. In addition, correlations for all hydrodynamic characteristics, viz. critical fluidization velocity, minimum velocity for full fluidization, maximum velocity for defluidization, peak pressure drop, fluctuation ratio, compressive force, and hysteresis have been developed some of which are proposed for the first time. La fluidisation gaz-solide revêt un vaste éventail d'applications industrielles comme les réactions catalytiques, la combustion, la gazéification, etc. Pour un certain nombre deces applications, il y a une réduction granulométrique durant l'activité menant à un entraînement età une limitation intenses de la vitesse de fonctionnement. Les divers problèmes liés aux particules de dimensions différentes ou aux dimensions de particules changeantes pourraient être surmontésen adoptant les lits coniques dans les activités de fluidisation. Dans le cadre de la présente étude, lephénomène de fluidisation dans les lits coniques a été évalué de façon critique au moyen devérifications expérimentales employant des particules de dimensions et de matières différentes et d'un vaste éventail d'angles de sommet de fluidiseurs. L'effet de la dimension des particules et del'angle des sommets sur le comportement de la fluidisation est nettement mis en évidence, ce quin'a pas été soulevé à venir jusqu'ici dans la documentation. L'importance de la force decompression qui existe dans les lits coniques est mise en évidence. De plus, les corrélations relativement à l'ensemble des caractéristiques hydrodynamiques, c.-à-d. la vitesse de fluidisation critique, la vitesse minimale de fluidisation complète, la vitesse maximale de défluidisation, la chute des pics de pression, le taux de fluctuation, la force de compression et l'hystérésis, ont été élaborées, certaines d'entre elles étant avancées pour la première fois. 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