• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 351
  • 141
  • 50
  • 49
  • 21
  • 9
  • 9
  • 9
  • 9
  • 9
  • 9
  • 6
  • 6
  • 6
  • 6
  • Tagged with
  • 850
  • 295
  • 106
  • 100
  • 84
  • 77
  • 75
  • 67
  • 58
  • 56
  • 51
  • 51
  • 50
  • 46
  • 44
  • 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

Improved Steam Assisted Gravity Drainage (SAGD) Performance with Solvent as Steam Additive

Li, Weiqiang 2010 December 1900 (has links)
Steam Assisted Gravity Drainage (SAGD) is used widely as a thermal recovery technique in Canada to produce a very viscous bitumen formation. The main research objectives of this simulation and experimental study are to investigate oil recovery mechanisms under SAGD process with different injection fluids, including steam, solvent or steam with solvent. 2D simulation studies based on typical Athabasca reservoir properties have been performed. Results show that a successful solvent co-injection design can utilize the advantages of solvent and steam. There is an optimal solvent type and concentration ratio range for a particular reservoir and operating condition. Long, continuous shale barriers located vertically above or near the wellbore delay production performance significantly. Co-injecting a multi-component solvent can flush out the oil in different areas with different drainage mechanisms from vaporized and liquid components. Placing an additional injector at the top of the reservoir results only in marginal improvement. The pure high-temperature diluent injection appears feasible, although further technical and economic evaluation of the process is required. A 2D scaled physical model was fabricated that represented in cross-section a half symmetry element of a typical SAGD drainage volume in Athabasca. The experimental results show co-injecting a solvent mixture of C7 and xylene with steam gives better production performance than the injection of pure steam or steam with C7 at the study condition. Compared to pure steam injection runs ( Run 0 and 1), coinjecting C7 (Run 2) with steam increases the ultimate recovery factor of oil inside the cell from 25 percent to 29 percent and decreases the ultimate CSOR from 2.2 to 1.9 and the ultimate CEOR from 4892 J/cm 3 to 4326 J/cm 3 ; coinjecting C7 and Xylene (Run 3) increases the ultimate recovery factor of oil from 25 percent to 34 percent, and decreases the ultimate CSOR 2.2 to 1.6 and the ultimate CEOR from 4892 J/cm 3 to 3629 J/cm 3 . Analyses of the experimental results indicate that partial pressure and the near wellbore flow play important roles in production performance. In conclusion, a successful solvent injection design can effectively improve the production performance of SAGD. Further research on evaluating the performance of various hydrocarbon types as steam additives is desirable and recommended.
42

The effect of solvents and processing conditions on the solvent extraction of coal

Bhole, Manish R. January 1900 (has links)
Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xiii, 122 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 100-103).
43

Pitch production using solvent extraction of coal suitability as carbon anode precursor /

Ali Pour, Mehdi Mohammad. January 2009 (has links)
Thesis (M. Sc.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Dec. 14, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Chemical Engineering, Department of Chemical and Materials Engineering, University of Alberta." Includes bibliographical references.
44

Solvent reclaiming by sulfate precipitation for CO2 capture

Rafique, Humera Abdul 04 June 2012 (has links)
Sulfate accumulates in the post-combustion CO₂ capture system and must be removed to re-use amine efficiently. Removal of sulfate from the amine-based postcombustion CO₂ capture system through a solvent reclaiming process may reduce CO₂ capture costs. This work determines the solubility of K₂SO₄ and Na₂SO₄ in 2 to 8 m PZ loaded with CO₂ and develops a thermodynamic and process model for the reclaiming process. At 40°C the solubility of Na2SO₄ in 8 m PZ with a CO₂ loading of 0.3 is 0.3 m Na2SO₄ and that of K₂SO₄ is 0.1 m K₂SO₄. Sulfate solubility in PZ solutions is represented by the empirical models: K₂SO₄: ln(Ksp) = 10.53I[superscript 0.3] - 0.98[PZ][subscript T] -3440/T - 2.42 ; Na₂SO₄: ln(Ksp) = 2.137I[superscript0.3] - .6505[PZ][subscript T] -826/T + 265 where [PZ][subscript T] = 2*(molality of PZ). A K₂SO₄ and Na₂SO₄ solubility thermodynamic model was developed in the eNRTL framework in the Fawkes model for PZ/CO₂/H₂O in Aspen Plus[trademark]. The energy cost of the Na process when removing the equivalent of 100 ppm SO₂ from the flue gas, ranging from $0.1-0.5/ton CO₂, was practically the same as the K process(ranging from $0.1-0.8/ton CO₂). The K₂SO₄ recovered in the process can be used as fertilizer. However, the KOH will still cost $0.6/tonne CO₂. If it is not possible to sell the K₂SO₄ as fertilizer because of the impurities that may be present on the K₂SO₄crystals, the chemical cost of the process would increase to $2/tonne CO₂. The chemical cost for the Na case is $0.7/tonne of CO₂. / text
45

Solute-solvent Interactions in Folded and Unfolded Proteins

Lee, Soyoung 31 August 2011 (has links)
This thesis is devoted to understanding solute-solvent interactions in folded and unfolded proteins. To this end, we have studied partial molar volume, Vo, and adiabatic compressibility, KoS, of 20 amino acid side chains using low weight molecular model compounds, N-acetyl amino acid amide and its derivatives, between 18 oC and 55 oC. We used our data to develop an additive scheme for calculating the partial specific volume and adiabatic compressibility of fully extended polypeptide chains as a function of pH and temperature. We compared our calculated volumetric characteristics of the fully extended conformations of apocytochrome c and apomyoglobin with the experimental values measured in neutral pH (for apocytochrome c) or acidic pH (for apomyoglobin). The comparison between the calculated and experimental volumetric characteristics suggested that neither apocytochrome c nor apomyoglobin are fully unfolded and retain solvent-inaccessible amino acid residues. To study cosolvent-solute interactions, we determined Vo and KoS of amino acid side chains and glycyl units as a function of urea concentration. We analyzed these data within the framework of a statistical thermodynamic formalism to determine the association constants, k, for the reaction in which urea binds to each of the amino acid side chains and the glycyl unit replacing two water molecules in solvation shell. Our determined k range from 0.04 to 0.39 M with the average of 0.16 ± 0.09 M. There was no apparent correlation between the values of k and the ratio of polar to nonpolar solvent accessible surface areas. This study supports a direct interaction model in which urea denatures a protein by concerted action via favorable interactions with a wide range of protein groups. In addition, we have presented buffer ionization effect on the volume of protein denaturation could be significant with the potential to affect not only its magnitude but also its sign using a pressure perturbation calorimetric technique. Our results identified buffer ionization as an important determinant of protein transition volume that needs to be carefully taken into account. Results described in this work provide fundamental understanding of solute-solvent interaction in both folded and unfolded proteins.
46

Solvent extraction of coal: Influence of solvent chemical structure on extraction yield and product composition

Rivolta, Mariangel Unknown Date
No description available.
47

Solute-solvent Interactions in Folded and Unfolded Proteins

Lee, Soyoung 31 August 2011 (has links)
This thesis is devoted to understanding solute-solvent interactions in folded and unfolded proteins. To this end, we have studied partial molar volume, Vo, and adiabatic compressibility, KoS, of 20 amino acid side chains using low weight molecular model compounds, N-acetyl amino acid amide and its derivatives, between 18 oC and 55 oC. We used our data to develop an additive scheme for calculating the partial specific volume and adiabatic compressibility of fully extended polypeptide chains as a function of pH and temperature. We compared our calculated volumetric characteristics of the fully extended conformations of apocytochrome c and apomyoglobin with the experimental values measured in neutral pH (for apocytochrome c) or acidic pH (for apomyoglobin). The comparison between the calculated and experimental volumetric characteristics suggested that neither apocytochrome c nor apomyoglobin are fully unfolded and retain solvent-inaccessible amino acid residues. To study cosolvent-solute interactions, we determined Vo and KoS of amino acid side chains and glycyl units as a function of urea concentration. We analyzed these data within the framework of a statistical thermodynamic formalism to determine the association constants, k, for the reaction in which urea binds to each of the amino acid side chains and the glycyl unit replacing two water molecules in solvation shell. Our determined k range from 0.04 to 0.39 M with the average of 0.16 ± 0.09 M. There was no apparent correlation between the values of k and the ratio of polar to nonpolar solvent accessible surface areas. This study supports a direct interaction model in which urea denatures a protein by concerted action via favorable interactions with a wide range of protein groups. In addition, we have presented buffer ionization effect on the volume of protein denaturation could be significant with the potential to affect not only its magnitude but also its sign using a pressure perturbation calorimetric technique. Our results identified buffer ionization as an important determinant of protein transition volume that needs to be carefully taken into account. Results described in this work provide fundamental understanding of solute-solvent interaction in both folded and unfolded proteins.
48

Spectroscopic and flow-injection studies of some novel ion-pair reactions

Barakat, Salem Ahmad Salem January 1991 (has links)
No description available.
49

Studies in solvent extraction chemistry and ion-selective electrodes /

Cattrall, R. W. January 1985 (has links) (PDF)
Thesis (D. Sc.)--University of Adelaide, Faculty of Science, 1985. / Consists mainly of offprints of articles by the author. Includes bibliographical references.
50

Carbon fuels for the direct carbon fuel cell

Saddawi, Abha. January 1900 (has links)
Thesis (M.S.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains ix, 71 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 52-53).

Page generated in 0.0609 seconds