Neste trabalho foram realizadas análises estruturais de dois conjuntos de vidros metafosfatos ternários relevantes em potenciais aplicações: aluminofosfatos e álcalis mistos. Para os aluminofosfatos a análise estrutural tem por objetivo verificar a existência de comportamentos preferenciais da conectividade entre os grupos fosfatos e os átomos de Al, e verificar a possível extensão a estes sistemas ternários de princípios de ligação química e ordem local inferidos em fosfatos binários, sendo os sistemas estudados K(1-x)Alx(PO3)(2x+1) e Na(1-x)Alx(PO3)(2x+1) . Para os vidros de álcalis mistos, a análise estrutural tem por objetivo identificar se existe segregação ou mistura aleatória das duas espécies de cátions, e determinar quais modificações na ordem local de cada álcali são induzidas pela troca de espécies, sendo os sistemas estudados LixNa(1-x)(PO3), KxNa(1-x)(PO3, RbxNa(1-x)(PO3), RbxLi(1-x)(PO3) e CsxLi(1-x)(PO3). As informações estruturais nestes vidros foram obtidas através de técnicas de Ressonância Magnética Nuclear (RMN) de estado sólido de 7Li, 23Na, 27Al, 31P, 87Rb e 133Cs. A conectividade entre a rede de fosfatos e os átomos de Al foi estudada utilizando informações a respeito da distribuição de espécies tetraédricas de fosfatos Q2m , sendo m = 0,1, 2 o número de pontes P-O-Al por tetraedro, obtidas através de RMN de 31P, e do número de coordenação médio do Al obtido através de RMN de 27Al. Da análise quantitativa da evolução das diferentes populações Q2m com a concentração de Al, juntamente com o número de coordenação médio do Al, foi possível verificar a existência de comportamentos preferenciais na organização estrutural: tetraedros fosfatos compartilham um vértice único (oxigênio não-ponte) com os poliedros de coordenação do Al. Esta organização de médio alcance é mantida até uma determinada concentração de Al, onde todo tetraedro forma uma ponte P-O-Al . A distribuição das espécies Q2m resultante é do tipo binária em função da concentração de Al: { Q20, Q21 } até concentrações intermediárias e { Q21, Q22 } para concentrações altas. Para os metafosfatos de álcalis mistos, o comportamento do desvio químico de 23 Na e 133Cs revela um efeito sistemático de aumento/decréscimo no tamanho do ambiente de coordenação ao redor dos álcalis em função da substituição. O ambiente de O dos álcalis de menor raio iônico resulta comprimido quando ocorre a substituição deste por uma espécie de raio iônico maior, e vice-versa. Com relação à distribuição dos álcalis na rede vítrea, as evoluções dos desvios químicos em função da substituição excluem a possibilidade de segregação dos álcalis ou separação de fase. A análise do acoplamento dipolar homonuclear de 23 Na, através da medida do segundo momento, revelou que a mistura de Na com o segundo álcali não é aleatória, existindo uma maior probabilidade de um Na ter outro Na como próximo vizinho. A correlação entre o grau de não-aleatoriedade na dispersão do Na e o incremento na magnitude do efeito de álcalis mistos na condutividade DC dos metafosfatos de Rb-Na, K-Na e Li-Na sugere que os fenômenos estão fundamentalmente relacionados. Esta seria a primeira evidência de vínculo entre uma propriedade estrutural da distribuição dos álcalis e o efeito de álcalis mistos de uma propriedade dinâmica. / In this work, the structure of two ternary metaphosphate glass systems was analyzed: aluminum-phosphates and mixed-alkali. The aim of the study in aluminum-phosphates is to determine the existence of preferential structural connectivities between phosphate groups and Al, and to verify the possible extension to these ternary glasses of principles of structural organization valid in binary phosphates. The aluminum metaphosphates studied here were K(1-x)Alx(PO3)(2x+1) and Na(1-x)Alx(PO3)(2x+1) . In mixed-alkali metaphosphates the goal of the structural analysis is the identification of the way in which alkali cations are distributed in the glass network (segregation versus random mixture), and to determine what kind of modification in the local order around the alkalis are induced by the substitution of species. The mixed-alkali metaphosphate studied here were LixNa(1-x)(PO3), KxNa(1-x)(PO3, RbxNa(1-x)(PO3), RbxLi(1-x)(PO3) and CsxLi(1-x)(PO3). The structural information was obtained using solid-state Nuclear Magnetic Resonance (NMR) techniques of 7Li, 23Na, 27Al, 31P, 87Rb and 133Cs. The connectivity between the phosphate groups and Al was analyzed studying the populations of phosphate species Q2m, with m=0,1,2 being the number of P-O-Al bridges per tetrahedron, obtained using 31P-NMR, and considering the average coordination number of Al obtained by 27Al-NMR. Through the quantitative analysis of the evolution of the Q2m population with the Al concentration, it was possible to identify the existence of a preferential structural behavior: phosphate tetrahedra share only one common corner (non-bridging oxygen) with the coordination polyhedra around Al. This medium-range organization can be sustained up to a certain concentration of Al, to the point where every phosphate establishes a P-O-Al bridge. The resulting distribution of Q2m species can be identified as binary, as a function of the Al content: { Q20, Q21} up to intermediate concentrations and { Q21, Q22} for higher concentrations. In the mixed-alkali metaphosphates, the behavior of the 23Na and 133Cs chemical shift reveals a systematic increase/decrease in the average size of the coordination environment around the alkalis as a function of the substitution. The O environment around cations with the smaller ionic radius is compressed as this species is substituted by another alkali with bigger ionic radius, and vice-versa. With respect to the alkali distribution in the glass network, the observed evolution of the chemical shift as a function of the cation substitution excludes the possibility of segregation of alkalis or phase separation. The analysis of the 23Na homonuclear magnetic dipolar coupling, through the measurement of the second moment, revealed that the mixture at atomic scale of Na with the second alkali is not random, having a higher probability of a Na being close to other Na than to other alkali. The correlation between the degree of non-random dispersion of Na and the increment in the magnitude of the mixed alkali effect in the dc conductivity of Rb-Na, K-Na and Li-Na metaphosphates indicates a fundamental connection between both phenomena. This may be the first evidence of a relation between a structural property of the alkali distribution and the mixed alkali effect of a dynamical property.

Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2017-06-29T12:25:26Z No. of bitstreams: 2 Dissertação - Geovanne Caetano Gomes - 2017.pdf: 4000475 bytes, checksum: 9ebf09d429582174011cbfd00331c5d4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-07-10T14:15:56Z (GMT) No. of bitstreams: 2 Dissertação - Geovanne Caetano Gomes - 2017.pdf: 4000475 bytes, checksum: 9ebf09d429582174011cbfd00331c5d4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-07-10T14:15:56Z (GMT). No. of bitstreams: 2 Dissertação - Geovanne Caetano Gomes - 2017.pdf: 4000475 bytes, checksum: 9ebf09d429582174011cbfd00331c5d4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-05-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Among the several deleterious actions may attack concrete elements, is the alkali-aggregate reaction (AAR), which affects, mainly, structures of dams, bridges and foundations, where the alkali-silica reaction (ASR) is the most common. One of the main challenges regarding the prediction of this phenomenon is the development of models that may predict damage specific for this reaction, which constitute the theme of this research. Firstly, a systematic literature review was conducted with respect to the models developed, with the organization and classification of the data found, presenting a clear and detailed state-of-art. Therefore, the studies published in journals in the last five years (2012-2016) were selected, in order to conduct their categorization regarding the scale and nature of the analysis, type of modeling, and the software necessary to execute the simulations, besides the summarizing, grouping and analysis of the information concerning the input data necessary to the execution of each modeling, as well as the results generated by each one of them. The models which do not predict damage, i.e. general models that simulate the ASR, were investigated to verify their contribution to a better understanding of the chemical and physical processes that occur in the concrete affect by the reaction. Finally, it was verified that the models analyzed are based on different theories and methods of analyses, demanding distinct input data and generating heterogeneous output data, which are meticulously explained in this paper. / Dentre as várias ações deletérias que podem atacar elementos de concreto tem-se a reação álcali-agregado (RAA), a qual afeta principalmente as estruturas de barragens, pontes e fundações, sendo a reação do tipo álcali-sílica (RAS) a mais recorrente nelas. Um dos principais desafios no que tange à predição desse fenômeno é o desenvolvimento de modelos de previsão de dano específicos dessa reação, constituindo-se o tema da presente pesquisa. A priori, executou-se uma revisão sistemática da literatura a respeito dos modelos desenvolvidos, com a organização e classificação dos dados encontrados, apresentando-se o estado da arte de forma clara e detalhada. Em seguida, foram elencados os trabalhos publicados em periódicos indexados nos últimos cinco anos (2012-2016), executando-se a categorização dos modelos quanto à escala e natureza de análise, tipo de modelagem, e softwares necessários para executar as simulações, além da sintetização, agrupamento e análise de informações concernentes aos dados de entrada necessários para a execução de cada modelação, bem como dos resultados gerados por elas. Para os modelos que não preveem dano, isto é, modelos gerais que simulam a RAS, investigou-se sua contribuição para o melhor entendimento dos processos químico-físicos que ocorrem no concreto afetado por ela. Verificou-se, assim, que os modelos analisados são pautados em diferentes teorias e métodos de análise, demandando dados de entrada distintos e gerando dados de saída heterogêneos, os quais são discriminados minuciosamente neste trabalho.

V mnoha oborech jsou stále využívána anorganická filtrační media založená na materiálech, jejichž výroba využívá primární suroviny. Jejich výroba je tedy energeticky náročná a v důsledku nákladná a neohleduplná k životnímu prostředí. Cílem této práce je ověřit možnost využití alkalicky aktivovaných materiálů na bázi sekundárních surovin, především vysokopecních strusek (BFS) a popílků z uhelných elektráren (FA), pro výrobu porézních médií schopných v budoucnosti nahradit keramické a jiné anorganické filtry. Výzkum je rozvinut skrze experimentální design založený na výpočetním schématu samostatně vyvinutém s pomocí programu MATLAB. Toto schéma počítá vhodná složení směsí na základě poměrů obsahu nejdůležitějších oxidů ve vstupních surovinách. Tak je zajištěno zohlednění proměnlivého složení vstupních surovin a práce je tím hodnotnější, že její výsledky jsou skrze početní nástroj zohledňující základní oxidové složení surovin zobecnitelné. Zároveň byly však pro srovnání a lepší názornost závislostí vlastností na složení navrhnuty a připraveny i série vzorků založené vždy pouze na jedné ze surovin. Z výsledků vyplývá, že pevnost vzorků z těchto směsí (vytvrzených 24 hodin při 70 °C) ve čtyřbodové ohybové zkoušce dle ČSN EN 12390 5 může přesáhnout 7,6 MPa. Dosažením co možná nejvyšší porozity však zákonitě negativně ovlivňuje pevnost materiálu a výsledný materiál tedy dosahuje pevnosti těsně nad hranicí 6,3 MPa. Výsledky obecně dokazují, že nejvíce je pevnost materiálů ovlivněna poměrem SiO2/Al2O3 a množstvím alkalického aktivátoru. Z výsledků vyplývá, že alkalicky aktivované materiály (AAM) na bázi strusky dosahují i více než dvojnásobné pevnosti analogických materiálů na bázi elektrárenského popílku. Velikost pórů materiálů připravených z tříděných surovin s velikostí zrna od desítek po lehce přes sto mikronů se ve většině případů pohybuje v rozmezí desetin ž jednotek mikronů, v případě výsledného materiálu je to pak přibližně 0,2 mikronu. Celková porozita lisovaných těles se pohybuje těsně pod 40 %, což je v tomto případě téměř dvojnásobek ve srovnání s totožnými materiály na bázi netříděných surovin. Výsledky rovněž ukazují, že materiály na bázi strusky vykazují nižší porozitu než ty na bázi popílku, což je patrně způsobeno rozdílnou morfologií částic obou materiálů – částice strusky jsou nepravidelně hranaté a částice popílku kulaté. V průběhu experimentální činnosti byla pozorována tvorba výkvětů u materiálů na bázi elektrárenských popílků. Pomocí Energo-disperzní spektroskopické analýzy (EDS) byly výkvěty identifikovány jako hydroxid sodný procházející karbonatací za účasti vzdušného CO2. Test permeability vyžadoval, kvůli velmi jemné povaze porézní struktury, přípravu asymetrických filtračních přepážek. Tyto přepážky dosáhli propustnosti 138 L/h.m2.bar pro vodu a 1320 L/h.m2.bar pro vzduch.

Recycled concrete is among the rising eco-friendly construction materials which helps to reduce waste and the need for new natural resources. However, such concrete may present previous deterioration due to, for instance, alkali-silica reaction (ASR), which is an ongoing distress mechanism that may keep being developed in the recycled material. This work aims to evaluate the potential of further distress and crack development (i.e. initiation and propagation) of AAR-affected RCA concrete in recycled mixtures displaying distinct past damage degrees and reactive aggregate types. Therefore, concrete specimens incorporating two highly reactive aggregates (Springhill coarse aggregate and Texas sand) were manufactured in the laboratory and stored in conditions enabling ASR development. The specimens were continuously monitored over time and once they reached marginal (0.05%) and very high (0.30%) expansion levels, they were crushed into RCA particles and re-used to fabricate RCA concrete. The RCA specimens were then placed in the same previous conditions and the “secondary” ASR-induced development monitored over time. Results show that the overall damage in ASR-affected RCA concrete is quite different from affected conventional concrete, especially with regards to the severely damaged RCA particles, where ASR is induced by a reactive coarse aggregate, as the RCA particle itself may present several levels of damage simultaneously caused by past/ongoing ASR and newly formed ASR. Moreover, the influence of the original damage extent in such RCA concrete was captured by the slightly damaged RCA mixture eventually reaching the same damage level as the severely damaged mixture. Furthermore, the original extent of deterioration influence the “secondary” induced expansion and damage of RCA concrete since the higher the original damage level, the higher the cracks numbers and lengths observed in the RCA concrete for the same expansion level whereas wider cracks are generated by RCA having previously been subjected to slight damage thus indicating the difference in the distress mechanism as a function of original extent of damage. In addition, it has been found that distress on RCA containing a reactive sand generates and propagates from the residual mortar (RM) into the new mortar (NM) as opposed to RCA containing a reactive coarse aggregate, being generated and propagated from the original coarse aggregate (i.e. original virgin aggregate – OVA) into the NM. Likewise, RCA containing a reactive sand caused longer and higher number of cracks for the same “secondary” induced expansion than the RCA made of reactive coarse aggregate. Finally, novel qualitative and descriptive models are proposed in this research to explain ASR-induced distress generation and propagation on RCA mixtures made of reactive fine and coarse aggregates.

Für viele Anwendungen in der Grundlagenforschung, Medizin und industriellen Entwicklung sind Beschleuniger der entscheidende Antrieb. Vor allem Elektronenbeschleuniger sind als Synchrotronquellen unter den brillantesten Quellen für Strahlung im Infrarot- bis Röntgenbereich und damit unerlässlich für eine Vielzahl von Anwendungen und analytischen Methoden. Photoinjektoren stellen als Elektronenquellen für Beschleuniger eine wichtige Komponente für die Entwicklung von Lichtquellen wie Freie-Elektronen-Laser, sowie für neue Beschleunigerkonzepte wie Linearbeschleuniger mit Energierückgewinnung dar. Die Photokathode und der Anregungslaser definieren dabei mit der Quantenausbeute (QE) und der intrinsischen Emittanz zentrale Kenngrößen des Photoinjektors. Diese Arbeit beschreibt die Entwicklung von Alkali-Antimonid Photokathoden für die Anwendung in einem Photoinjektor mit supraleitendem Hochfrequenz-Resonator. Alkali Antimonide zeigen generell eine hohe QE und Cäsium Kalium Antimonid (Cs-K-Sb) im speziellen verspricht eine geringe intrinsische Emittanz aufgrund der Ionisierungsenergie, die nur knapp unter der Photonenenergie der grünen Anregungslaser liegt. Mit der Inbetriebnahme eines Präparations- und Analysesystems konnte die Abscheidung dünner Schichten von Cs-K-Sb sowie die Messung der QE und chemischen Zusammensetzung erzielt werden. Dabei wurde mit der Ko-evaporation der Alkalimetalle eine neue Wachstumsmethode etabliert und hinsichtlich der Prozessstabilität und Qualität der erzeugten Proben mit der sequenziellen Methode verglichen. Schließlich beschreiben die Inbetriebnahme eines Prototyps des Photoinjektors und erste erfolgreiche Kathodentransfers im Vakuum einen wichtigen Schritt hin zum Betrieb eines Beschleunigers mit einer Cs-K-Sb Photokathode im supraleitenden Hochfrequenz-Injektor. Diese Kombination erlaubt die Erzeugung eines Elektronenstrahls mit niedriger Emittanz und hohem mittleren Strom. / For many disciplines in basic and applied research, medicine and industrial development accelerators are an important driving force. Especially electron accelerators as synchrotron sources are among the brightest sources of radiation from the infrared to the X-ray regime and thus fundamental to a broad range of analytical techniques. Photoinjectors as electron sources for accelerator applications are a key component for the development of light sources such as free electron lasers as well as new accelerator concepts like energy-recovery linacs. The photocathode and drive laser define the quantum efficiency (QE) and intrinsic emittance of the photoemission process and thus central figures of merit of the photoinjector. This work focuses on the development of alkali antimonide photocathodes for the application in a superconducting radio frequency photoinjector. Alkali antimonides generally exhibit a high QE and cesium potassium antimonide (Cs-K-Sb) specifically is expected to release electrons with a low intrinsic emittance as the photoemission threshold is close to the photon energy of common, green, drive laser wavelengths. A preparation and analysis system has been commissioned for the deposition of Cs-K-Sb thin film photocathodes and their analysis regarding QE and chemical composition. A new deposition technique, the alkali metal co-deposition, was established and compared to the sequential deposition in terms of process reliability and quality of the produced samples. The work concludes with a report of the commissioning of a prototype of the photoinjector and successful cathode transfers in ultra-high vacuum, which represents an important technological advancement towards the operation of an accelerator with the combination of Cs-K-Sb photocathodes and an SRF injector. This combination makes the generation of an electron beam with low emittance and high average current possible.

No description available.

The chemical company Perstorp AB has a 50 MWth circulating fluidized bed to supply the production plant with process steam. The fuel mixture used shows a large variation with about 20 different fuel fractions that can be divided into the categories, residue wood chips, sludge, forest fuel, animal waste, industrial residues, and peat. From an economic and environmental perspective, the use of peat should be minimized because it is classified as a fossil fuel. Peat has positive combustion characteristics due to a combination of sulfur and silica based minerals that can reduce alkali chloride related corrosion. Therefore it is not always possible phase out peat without negatively affecting the boilers availability. Besides reducing CO2 emissions, it is desirable to reduce the use of additives such as limestone and to use cheap waste fractions as fuels when operating a boiler. Similar to peat, reduced use of limestone and the introduction of a new waste fractions can affect the boiler availability negatively. If less limestone is used the risk of agglomeration can increase and often waste products can contain ash elements problematic in both a agglomeration and corrosion perspective.The aim of this master thesis is to investigate the possibility of reducing the usage of peat by minimizing the limestone content and to see if it would be possible to add a new Na-rich waste fraction to the fuel mixture. This was investigated by determining first what fuels that are used and in what amounts. Each fuel was either sent for new elemental analysis or existing analyses were used depending on if it was deemed to be still representative. With the help of experienced personnel working with the boiler, future possible cases for fuel mixtures could be determined: Case 1. Replacing peat with forest fuels. Case 2. Replacing peat with residue wood chips. Case 3. Replacing both peat and animal waste with residue wood chips. Case 4. Introducing Na-rich fuel. The theoretical available SO2 content could be determined for each case and three limestone levels. For each case the CO2 emissions and the economic savings could be estimated when the peat were fully removed and the limestone content halved. From an SO2 perspective, the results indicate that it could be possible to phase out peat for cases 1-2 by adjusting the limestone levels but this would not be enough for case 3. Adding the Na-rich fuel could also be problematic and more investigation has to be put into potential additives and fuels to compensate for the additional Na.When peat is fully phased out in case 1-3 the CO2 emission would decrease by 10 000 tonCO2/year. Due to the cost of CO2 emissions, this could result in considerable monetary savings. From the results it is estimated that case 1 could save 9.1 million SEK/year, case 2 10.3 million SEK/year, and case 3 6.5 million SEK/year when the peat is fully removed. This does not include changes in availability and maintenance costs. / Kemiindustriföretaget Perstorp AB har en 50 MWth cirkulerande fluidiserad bädd panna för att förse produktionen med processånga. Bränsleblandningen som används visar en stor variation med ett 20-tal olika bränslefraktioner som kan delas in i kategorierna returflis (RT-flis), slam, skogsbränsle, slaktrester, industrirester och torv. Från ett ekonomiskt- och miljöperspektiv bör användningen av torv minimeras eftersom den är klassad som ett fossilt bränsle. Dock har torv positiva förbränningsegenskaper vilket beror på dess innehåll av såväl svavel som kiselbaserade mineraler vilka minskar korrosions förmågan för alkali-klorider. Därför är det inte alltid möjligt att fasa ut torven utan att riskera att försämra pannans tillgänglighet. Andra aspekter förutom minskade CO2 utsläpp som är fördelaktiga vid drift av en panna, är att minimera användningen av tillsatser som kalksten samt använda restprodukter som bränsle i största möjliga mån. Dock kan, som i fallet med torv, en minskad användning av kalksten och ett nytt restproduktbränsle ha potentiella negativa konsekvenser för pannans tillgänglighet. Om kalksten används i mindre utsträckning kan risken för klumpbildning i pannan, agglomerering, öka och ofta kan restprodukter från produktionen innehålla höga halter av problematiska grundämnen både i ett korrosions och agglomererings perspektiv.Syftet med detta examensarbete har varit att undersöka möjligheterna att minska användningen av torv och kalksten samt möjligheten att tillföra ett nytt Na-rikt bränsle till bränsleblandningen. Detta undersöktes genom att först bestämma vad som eldades och i vilka mängder. Genom att använda data från leveransrapporter (för bränslen och additiv) och bränsleanalyser. I de fall det fanns representativ bränsleanalys användes dessa, i övrigt provtogs och beställdes nya bränsleanalyser. Med hjälp av erfaren personal som jobbar med pannan kunde olika möjliga framtida bränsleblandningar bestämmas. Dessa bränsleblandningar delades in i olika scenarion eller case som det kallas här: Case 1. Ersätta torv med skogsbränsle. Case 2. Ersätta torv med RT-flis. Case 3. Ersätta både torv och biomal (slaktrester) med RT-flis. Case 4. Introduktion av Na-rikt restbränsle. Baserat på en tidigare kartläggning av askomvandlingen i pannan kunde det teoretiska tillgängliga SO2 halten i rökgaserna bestämmas för varje case för tre olika kalkstenshalter. För varje case kunde sedan CO2 utsläppen samt de ekonomiska besparingarna estimeras då torv var helt urfasad och kalkstensinnehållet halverat. Från ett SO2 perspektiv pekar resultaten på att det skulle vara möjligt att fasa ut torven helt genom att minska kalkstenen mellan 0-50 vikt% för case 1 och 2 men inte för case 3. Att tillsätta det Na-rika bränslet kan potentiellt vara problematiskt. För att elda detta Na-rika bränslet kan det krävas en ny additiv eller ett S-rikt bränsle för att balansera tillskottet av Na och därmed minska korrosionsrisken.Vid utfasning av samtlig torv minskar CO2 utsläppen i case 1-3 med runt 10 000 tonCO2/år. Eftersom utsläpp av fossil CO2 är beskattat, uppskattas de möjliga besparingarna som betydande, 9.1 miljoner SEK/år i case 1, 10.3 miljoner SEK/år case 2 och 6.5 miljoner SEK/år i case 3 inklusive inköps- och askhanteringskostnader.

Thesis: Elec. E., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 1981 / Includes bibliographical references. / by Mansour Shayegan. / Elec. E. / Elec. E. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science

Master of Science / Department of Grain Science and Industry / Praveen V. Vadlani / In our study, five different bioenergy crops: wheat straw (Triticum aestivum), forage sorghum stover (sorghum bicolor), switchgrass (Panicum virgatum), miscanthus (Miscanthus giganteus) and sweet sorghum baggase (Sorghum bicolor) were evaluated for bio-ethanol production at 20% (w/v) initial substrate concentration under separate hydrolysis and fermentation (SHF) process. The substrates were ground to pass through 600µm mesh size and treated with 2% (w/v) NaOH at 121oC for 30 minutes. The washed and neutralized pretreated residues were subjected to saccharification using cellulase and β-glucosidase enzymes (ratio 1:1.25) at concentrations of 25 filter paper unit (fpu)/g and 31.25fpu/g, respectively, in pH 5.0 citrate buffer in an orbital incubator shaker at 150 rpm for 72 h. The hydrolysate obtained was centrifuged and supernatant was collected for fermentation. Fermentation was performed in shake flasks using Saccharomyces cerevisiae at 10% (w/v) inoculum concentration at 100 rpm for 24 h. Alkali treatment was effective in delignification of all the biomass feedstocks. The highest percent removal on raw biomass basis was attained for sorghum stover BMR-DP (81.3%, w/w) followed by miscanthus (79.9%, w/w), sorghum stover BMR-RL (69.2 %, w/w), wheat straw (68.0 %, w/w), switchgrass (66.0%, w/w), and sorghum baggase (65.4%, w/w). Glucan saccharification varied from 56.4-72.6 % (w/w) corresponding to a glucose levels of 0.45-0.34 g/g of dry substrate. Highest saccharification was observed for wheat straw while lowest was observed for miscanthus after 48 hours of hydrolysis. A maximum final ethanol concentration of 4.3% (w/v) was observed for wheat straw followed by sorghum baggase (4.2%), sorghum RL-BMR (3.6%), miscanthus (3.4%), sorghum DP-BMR (3.4%), and switchgrass (3.2%). From our studies, it is evident that high substrate concentration used for enzymatic hydrolysis was able to provide high final ethanol concentration. The lignin content and its arrangement in different biomass feedstocks may have affected saccharification and subsequent ethanol production. Bulk density and flowability are the two major key parameters that should be addressed to reduce processing cost of biomass for bioethanol production. Pelleting of biomass can increase the bulk density, thereby reducing the handling and transportation costs. In addition to above study, I analyzed the changes in chemical composition due to pelletization and pretreatment, and its effect on ethanol production by comparing unpelleted and pelleted biomass ethanol production efficiency. Wheat straw and big bluestem pelleted and unpelleted biomass were compared for their ethanol production efficiency. Pelleted and unpelleted wheat straw (Triticum aestivum) and bigblue stem (Andropogon gerardii Vitman) at a substrate concentration of 10% (w/v) were subjected to 2% NaOH treatment at 1210C for 30 min and the resulting residues were analyzed for changes in chemical composition. Saccharification of residue was done at substrate concentration of 12% (w/v) for 48 h. The sugars obtained were fermented to ethanol using Saccharomyces cerevisiae. Pelletization did not significantly affect the chemical composition of biomass in terms of glucan, xylan and lignin content. Delignification of pelleted biomass was greater than unpelleted biomass. Pelletization did not influence final ethanol production for both substrates.

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