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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Elucidating the solid, liquid and gaseous products from batch pyrolysis of cotton-gin trash.

Aquino, Froilan Ludana 15 May 2009 (has links)
Cotton-gin trash (CGT) was pyrolyzed at different temperatures and reaction times using an externally-heated batch reactor. The average yields of output products (solid/char, liquid/bio-oil, and gaseous) were determined. The heating value (HV) of CGT was measured to be around 15-16 MJ kg- 1 (6500-7000 Btu lb-1). In the first set of tests, CGT was pyrolyzed at 600, 700, and 800°C and at 30, 45, and 60 min reaction period. The maximum char yield of 40% by weight (wt.%) was determined at 600°C and 30 min settings, however, the HV of char was low and almost similar to the HV of CGT. A maximum gas yield of 40 wt.% was measured at 800°C and 60 min and the highest liquid yield of 30 wt.% was determined at 800°C and 30 min. In the modified pyrolysis test, the effects of temperature (500, 600, 700, and 800°C) on the product yield and other properties were investigated. The experiment was performed using the same reactor purged with nitrogen at a rate of 1000 cm3 min-1. Gas yield increased as temperature was increased while the effect was opposite on char yield. The maximum char yield of 38 wt.% was determined at 500°C and 30 min. The char had the largest fraction in the energy output (70-83%) followed by gas (10-20%) and bio-oil (7- 9%). Maximum gas yield of 35 wt.% was determined at 800°C. The average yield of CO, H2 and total hydrocarbons (THC) generally increased with increased temperature but CO2 production decreased. Methane, ethane, and propane dominated the THC. The bio-oil yield at 600°C was the highest at about 30 wt.% among the temperature settings. The HV of bio-oil was low (2-5 MJ kg-1) due to minimal non-HC compounds and high moisture content (MC). A simple energy balance of the process was performed. The process was considered energy intensive due to the high amount of energy input (6100 kJ) while generating a maximum energy output of only 10%. After disregarding the energy used for preparation and pyrolysis, the energy losses ranged from 30-46% while the energy of the output represent between 55-70% of the input energy from CGT.
42

The Role of the TM2-HAMP Junction in Control of the Signaling State of the Aspartate Chemoreceptor of E. coli

Wright, Gus Alan 2009 August 1900 (has links)
The mechanism of allosteric coupling between the external ligand-binding domain and the internal signaling domain of bacterial chemoreceptors is poorly understood. Genetic, biochemical, and biophysical evidence suggests that transmembrane helix 2 (TM2) undergoes a piston-like displacement of approximately 1-3 Angstroms toward the cytoplasm upon the binding of aspartate to the Tar receptor. The signal is then transmitted to the cytoplasmic signaling domain via the HAMP domain, a conserved motif found in all methyl-accepting chemotaxis proteins (MCPs) and most histidine protein kinases (HPKs). HAMP forms a parallel four-helix bundle consisting of a dimer of two amphipathic helices (AS1 and AS2) connected by a flexible linker. The MLLT sequence between residues Arg-214, at the end of TM2, and the conserved residue Pro-219, at the beginning of AS1 of the HAMP domain (the TM2-HAMP junction), is predicted to be able to form a helical extension of TM2. We hypothesized that perturbing the native secondary structure and/or the length of the TM2-HAMP junction would disrupt the ability of HAMP to communicate the input signal from TM2 to the kinase-control domain. To test this hypothesis, we designed two experiments. First, constructs were made in which 1 to 3 Gly residues were inserted between T218 and P219. Second, Tar variants were constructed in which 1 to 9 Gly residues were inserted between R214 and P219. The results suggest that increasing the length and flexibility of the TM2-HAMP connection tends to uncouple signal propagation between the TM2 and the HAMP elements and suggests that HAMP alone causes an inhibitory effect on the cytoplasmic signaling domain. To determine whether the predicted helical register of the MLLT sequence is an important component of the propagation of the transmembrane signal from TM2 to the HAMP domain, we added and subtracted helical residues to the MLLT sequence. The results suggest that helical register and length of the TM2-HAMP junction are essential for optimal receptor function.
43

Tarring maintenance of Norwegian medieval stave churches : characterisation of pine tar during kiln-production, experimental coating procedures and weathering /

Egenberg, Inger Marie. January 2003 (has links)
Thesis (doctoral)--Göteborg University, 2003. / Includes bibliographical references (p. 137-157).
44

Rapid densification of the oil sands mature fine tailings (MFT) by microbial activity

Guo, Chengmai. January 2009 (has links)
Thesis (Ph.D.)--University of Alberta, 2009. / Title from PDF file main screen (viewed on Feb. 19, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Geotechnical Engineering, [Department of] Civil and Environmental Engineering, University of Alberta. Includes bibliographical references.
45

Characterizing the Transport of Process-Affected Water Contained in Oil Sands Tailings Ponds into the underlying Pleistocene clay till in Northern Alberta’s Athabasca Oil Sands region: A Field Study

Abolfazlzadehdoshanbehbazari, Mostafa Unknown Date
No description available.
46

Biomass gasification in ABFB : Tar mitigation

Vera, Nemanova January 2014 (has links)
Biomass gasification may be an attractive alternative for meeting future energy demand. Although gasification is a mature technology, it has yet to be fully commercialised due to tar formation. This study focuses on the tar mitigation in gas produced in an atmospheric bubbling fluidised bed (ABFB) gasification system. Previous studies indicated significant tar variability along the system. In this work the experimental procedure has been improved for reliable results and better understanding of tar variability in the producer gas. After having introduced a new sample point for tar analysis to the system, experimental results indicated tar reduction in the gasifier, probably due to continuous accumulation of char and ash in the bed, as well as in the ceramic filter owing to thermal and catalytic effects. Iron-based materials, provided by Höganäs AB, were applied in a secondary catalytic bed reactor for tar decomposition in the producer gas. It was found that tar concentration depends on catalytic and gasification temperatures and catalyst material. When changing the gasification temperature from 850 °C to 800 °C the conditions in the producer gas also changed from reductive to oxidative, transforming the initial metallic state of catalyst into its oxidised form. It may be concluded that the catalysts in their metallic states in general exhibit a better tar cracking capacity than their corresponding oxides. Due to the low reactivity of petroleum coke, an alternative may be to convert it in combination with other fuels such as biomass. Co-gasification of petroleum coke and biomass was studied in this work. Biomass ash in the blends was found to have a catalytic effect on the reactivity of petroleum coke during co-gasification. Furthermore, this synergetic effect between biomass and petcoke was observed in the kinetics data. / <p>QC 20141022</p>
47

The use of the waste delisting process - case study : the management of ferrochrome slag as a construction product in South Africa / Heather Booysen.

Booysen, Heather-Ann January 2008 (has links)
Ferrochrome slag is a by-product from the production of ferrochrome, an essential component in stainless steel. World wide it is known that ferrochrome slags are been used mainly in the road and civil construction industries, and in producing refractories. Slag management at ferrochrome producing companies has been influenced by the limited space available and financial cost implications of the siag dumps. In South Africa, according to the Department of Water Affairs and Forestry's minimum requirements, (DWAF, 1998), ferrochrome slag due to its quantity or volume on the disposal sites has been classified as hazardous, as it leaches Manganese (Mn) (33%) above the DWAF minimum environmental requirements acceptable levels. This rating of the slag has therefore put limitations on the use of slag commercially. This paper investigates the various slag uses proposed which can impact positively on the management of the slag i.e. that would reduce its dumping loads and consequently its impact on the surrounding environment. The uses proposed for are brick and concrete making and road building. The paper provides results for the proposed slag uses leaching potential, performs a risk assessment to determine its potential effect on the environment and human health as weli as discusses the method used to delist the slag through the South African delisting process. Comments on the process from the DEAT are also provided. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2009.
48

The use of the waste delisting process - case study : the management of ferrochrome slag as a construction product in South Africa / Heather Booysen.

Booysen, Heather-Ann January 2008 (has links)
Ferrochrome slag is a by-product from the production of ferrochrome, an essential component in stainless steel. World wide it is known that ferrochrome slags are been used mainly in the road and civil construction industries, and in producing refractories. Slag management at ferrochrome producing companies has been influenced by the limited space available and financial cost implications of the siag dumps. In South Africa, according to the Department of Water Affairs and Forestry's minimum requirements, (DWAF, 1998), ferrochrome slag due to its quantity or volume on the disposal sites has been classified as hazardous, as it leaches Manganese (Mn) (33%) above the DWAF minimum environmental requirements acceptable levels. This rating of the slag has therefore put limitations on the use of slag commercially. This paper investigates the various slag uses proposed which can impact positively on the management of the slag i.e. that would reduce its dumping loads and consequently its impact on the surrounding environment. The uses proposed for are brick and concrete making and road building. The paper provides results for the proposed slag uses leaching potential, performs a risk assessment to determine its potential effect on the environment and human health as weli as discusses the method used to delist the slag through the South African delisting process. Comments on the process from the DEAT are also provided. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2009.
49

The quality of binder-filler interfaces in carbon electrodes

Ogden, Gary N. January 1995 (has links)
The aims of this research project were to identify and classify the binder-filler interfaces formed in carbon electrodes and to determine the effects of the interfacial quality on important electrode properties. The effects of raw materials and some fabrication process variables on interfacial characteristics and quality of laboratory produced test electrodes were also studied, and the development of binder-filler interfaces during the carbonisation process followed. Electrode quality was assessed by measurement of density, electrical resistivity and tensile strength. Pore structural data were also obtained by using a computerised image analysis system allied to an optical microscope. Interface quality data were obtained by examining etched surfaces in a scanning electron microscope and classifying the binder-filler interface observed into one of five categories. The category depending on the extent of contact between the binder and filler. Accordingly, test electrodes were produced from combinations of four filler carbons, comprising three grades of calcined petroleum coke and an electro-calcined anthracite, and four coal-tar binder pitches which varied in the type and quantity of insoluble matter content. Examination of these test electrodes showed that the nature of the filler carbon used had a dominant influence on the quality of the interface formed, as assessed by this technique. A combination of one filler carbon and one binder pitch was used to study the effects of some fabrication process variables. These were pitch content and, mixing time and temperature. Of these process variables, pitch content and mixing temperature were found to have the major effects on the binder-filler interface and electrode quality. Investigation of the development of the binder-filler interfaces during the carbonisation process showed three distinct zones of interface development and transformation. These zones were associated with three temperature dependent mechanisms; thermal stress relaxation between 200-350 degrees C, volatile gas evolution from coal-tar pitch decompositionb etween3 50-600 degrees C and stresses induced by thermal contraction of the binder phase between 600-1000 degrees C.
50

Investigation of Hybrid Steam/Solvent Injection to Improve the Efficiency of the SAGD Process

Ardali, Mojtaba 03 October 2013 (has links)
Steam assisted gravity drainage (SAGD) has been demonstrated as a proven technology to unlock heavy oil and bitumen in Canadian reservoirs. Given the large energy requirements and volumes of emitted greenhouse gases from SAGD processes, there is a strong motivation to develop enhanced oil recovery processes with lower energy and emission intensities. In this study, the addition of solvents to steam has been examined to reduce the energy intensity of the SAGD process. Higher oil recovery, accelerated oil production rate, reduced steam-to-oil ratio, and more favorable economics are expected from the addition of suitable hydrocarbon additives to steam. A systematic approach was used to develop an effective hybrid steam/solvent injection to improve the SAGD process. Initially, an extensive parametric simulation study was carried out to find the suitable hydrocarbon additives and injection strategies. Simulation studies aim to narrow down hybrid steam/solvent processes, design suitable solvent type and concentration, and explain the mechanism of solvent addition to steam. In the experimental phase, the most promising solvents (n-hexane and n-heptane) were used with different injection strategies. Steam and hydrocarbon additives were injected in continuous or alternating schemes. The results of the integrated experimental and simulation study were used to better understand the mechanism of hybrid steam/solvent processes. Experimental and simulation results show that solvent co-injection with steam leads to a process with higher oil production, better oil recovery, and less energy intensity with more favorable economy. Solvent choice for hybrid steam/solvent injection is not solely dependent on the mobility improvement capability of the solvents but also reservoir properties and operational conditions such as operating pressure and injection strategy. Pure heated solvent injection requires significant quantities. A vaporized solvent chamber is not sustainable due to low latent heat of the solvents. Alternating steam and solvent injection provides heat for the solvent cycles and increases oil recovery. Co-injection of small volumes (5-15% by volume) of suitable solvents at the early times of the SAGD operation considerably improves the economics of the SAGD process.

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