Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains viii, 162 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 138-142).

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Dr. David S. Sholl; Committee Member: Dr. Andrei G. Fedorov; Committee Member: Dr. Ronald R. Chance; Committee Member: Dr. Victor Breedveld; Committee Member: Dr. William Koros. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Hydrogen could replace fossil fuels for power generation and transportation and contribute to a low carbon economy. However, current methods of producing hydrogen e.g. steam methane reformation of natural gas are not sustainable and also contribute to COi emissions. Dark fermentation of carbohydrate-rich waste organics and energy crops to hydrogen using mixed microflora could contribute to the mix of technologies for producing hydrogen sustainably. Naturally available mixed microflora can be enriched e.g. by heat treatment to select for hydrogen producers, typically clostridia. Fermentation endproducts from the hydrogen-producing stage could be fed to a second anaerobic digestion stage to recover more energy as methane and to stabilise the effluent. Although anaerobic digestion is well established, fermentative hydrogen production is not. This work evaluated the feasibility of hydrogen production from two energy crops, grass and fodder maize in batch culture without pretreatment; investigated the effect of increase in substrate (sucrose) concentration, attractive from an energy point of view, on the yield and stability of hydrogen production in continuous culture; examined the performance of a mesophilic high rate anaerobic digester treating effluent from a continuous hydrogen-producing bioreactor; demonstrated the possibility of changeover of substrate - sucrose, starch and xylose - during continuous hydrogen production and evaluated the effect of sparging with CO2 , a process gas, on hydrogen production. It was demonstrated for the first time that hydrogen production from grass and fodder maize by direct fermentation in batch culture (2.3 L reactor, 35°C, pH 5.2-5.3) is possible, with hydrogen yields of 75.6 ml/g dry matter wilted perennial rye grass and62.4 ml/g dry matter of fodder maize. In continuous culture (pH 5.2-5.3, 35°C, 12 hour hydraulic retention time (HRT)), stable hydrogen production was achieved up to 40 g/L sucrose concentration - with decreasing hydrogen yields, from 1.7±0.2 mol/mol hexose added at 10 g/L to 1.2±0.3 mol/mol hexose at 40 g/L - beyond which the system became unstable. The decrease in hydrogen yield and lack of stability at higher substrate concentrations was attributed to feedback inhibition by volatile fatty acids (VFAs). Effluent from the hydrogen reactor was readily degraded in an upflow anaerobic filter up to an organic loading rate of 10 gCOD/L/d (2 d HRT) and/or a sodium concentration of 1.87 g/L. Reduction of sodium levels in the methane reactor by using calcium hydroxide as alkali in the hydrogen reactor was found to extend the efficiency of degradation of VFAs; overall COD reduction for the two stage system fed with 20 g/L sucrose increased from 83% (with NaOH as alkali) to 91% with Ca(OH)2 . It was easier to switch from starch to sucrose and vice versa during continuous hydrogen production; however switching from sucrose or starch to xylose was slower, requiring operation for about 1 day in batch culture before continuous operation could commence. Sparging with CO2 improved hydrogen yield from sucrose by at least 71% and appeared to inhibit homoacetogenesis from starch. This work verifies the potential technical feasibility of generating hydrogen, a clean energy carrier, sustainably from carbohydrate-rich waste organics and energy crops.

>Magister Scientiae - MSc / Hydrogen has been regarded as an ideal energy carrier for future, it can be stored as a liquid in cryogenic tanks, a gas in high pressure cylinders and as solid in metal hydrides. Hydrogen storage in metal hydrides is of research interest because hydrides often have high energy density than gas or liquid hydrogen and are relatively safe. Ti and Ti alloys are promising hydrogen storage material because they have high affinity for hydrogen, light in weight and react reversibly with hydrogen. This work aims to investigate the hydrogen storage capacity of CP- Ti and Ti6Al4V alloy and Pd/Ti6Al4V alloy, where Pd was deposited on Ti6Al4V alloy. Samples were hydrogenated from room temperature to 650 °C at atmospheric pressure in the vacuum furnace under the 15%H/Ar atmosphere. Hydrogenation was carried out for a period of 3 hours for all samples. Sample composition and layer thickness were determined using Rutherford backscattering spectrometry. The microstructure and phase transformation were investigated using optical microscopy and X-ray diffraction technique. Hydrogen storage capacity was determined using elastic recoil detection analysis and gravimetric method. It was found that hydrogenation temperature has an effect on hydrogen absorption, microstructure and phase transformation. Maximum hydrogen concentration was obtained at hydrogenation temperatures of 550 °C for all materials with 45.57 at.% in CP-Ti, 34.77 at.% in Ti6Al4V alloy and 39 at.% H in Pd/Ti6Al4V coated system. In CP-Ti it was found that hydrogen absorption begins at 550 °C and decreases at hydrogenation temperature of 650 °C and that hydrogenation at both temperatures leads to formation of titanium hydrides and needlelike microstructure. At temperatures below 550 °C no hydrides were formed. For Ti6Al4V alloy ERDA results showed that no significant hydrogen absorption occurred at temperatures below 550 °C and at hydrogenation temperature of 650 °C, hydrogen absorption decreased drastically. The δ- titanium hydride was detected in the sample hydrogenated at 550 °C. Fine needle like microstructure was observed in the sample hydrogenated at 550 °C, and at higher temperature (650 °C ) coarse needles were formed. Pd coatings on Ti6Al4V alloy was found to increase the absorption of hydrogen, and allowing hydrogen to be absorbed at low temperatures. / National Research Foundation (NRF)

This thesis reports the outcome of a simulation study that examines the feasibility of using hydrogen peroxide as an alternative oxidant in the autothermal reforming (ATR) of diesel. The primary objective is to compare hydrogen peroxide's performance against conventional oxidants in reforming, focusing on product distribution and three pivotal process properties: diesel conversion, hydrogen production, and ethylene generation. The study further investigates the influence of the heat of decomposition on the performance and reaction routes of different oxidants. Additionally, a comparative analysis is conducted on the reforming performance in different reformer configurations, specifically contrasting a combined-reformer-configuration with a catalytic-reformer configuration. The ANSYS Chemkin-Pro is utilized to understand the potential benefits and challenges of the proposed approached. A reduced chemical mechanism of N-heptane/Toluene reforming as a surrogate for diesel, combined with a detailed surface reaction mechanism of propene on a three-way Pt/Rh catalyst are used in this study. It is found that the use of hydrogen peroxide as an oxidant demonstrated a complete fuel conversion and 183% higher hydrogen yield when compared with conventional oxidants. It also led to a 12% lower generation of ethylene, a precursor for coke formation. The catalytic-reformer configuration showed superior performance over the combined-reformer-configuration in terms of hydrogen yield. The insights from this study offer valuable perspectives on the feasibility and efficiency of using hydrogen peroxide as an alternative oxidant in the ATR of diesel, paving the way for potential advancements in the field.

This Master's thesis aims to examine Canada's historical and contemporary attempts to establish a sustainable hydrogen market in Canada. Specifically, my research sought to answer whether hydrogen is poised to take off within the current hype cycle or will be stifled, such as in previous attempts. My research aimed to explore this question by examining and comparing historical and contemporary literature relevant to hydrogen development in Canada. My research utilized an ESPELT analysis and involved interviewing multiple experts from across the country to reveal any nuances that underline the barriers and opportunities for determining the viability of Canada's domestic hydrogen market within the contemporary context.

The aim of this research is to identify problematic microstructural features as hydrogen traps in linepipe steel that serve to increase the hydrogen embrittlement susceptibility. A comparison is made between the hydrogen trapping capacity and associated hydrogen embrittlement susceptibility of Ca-treated X60 grade steel skelp and X70 grade steel skelp: the latter typically being more susceptible to hydrogen-induced cracking in sour environments. Through-thickness variations in the steel skelp microstructure were characterized across multi-length scales using light optical microscopy (LOM) and scanning electron microscopy (SEM) equipped with X-ray energy dispersive spectroscopy (EDS). Key features under study include the composition, shape, and distribution of non-metallic inclusions, as well as differences in features present between the quarterline (¼ and ¾ depths) and centerline (½ depth) microstructures. The type, count, and average size of inclusions present in both steel skelp grades were analyzed using an automated SEM-EDS technique called ASPEX®. Major types of inclusions detected in both grades of steel skelp include those containing Ca, Al, Mn, Mg and Ti as major elements. Overall, the area fraction of inclusions detected in the X70 steel was larger than those detected in the X60 with the exception of Ti-containing inclusions, which had a larger area fraction within the X60 steel. Comparing the number of detected inclusions shows that there was overall slightly less Ca-containing inclusions and significantly less Ti-containing inclusions detected in the X70 steel but there was generally more Al-containing, Mg-containing, and Mn-containing inclusions than those detected in the X60 steel. Thermal desorption spectroscopy (TDS) measurements were made on samples prepared from the ¼, ½, and ¾ depths of X60 and X70 steel skelps after galvanostatic cathodic charging in an As2O3-containing solution using an applied current density of −10 mA/cm2. Hydrogen release was measured using a HYDROSEEL® probe while the sample was heated from 20°C to 650°C to detect temperature values at which hydrogen gas release peaks occurred, and thus provide information on types of reversible and/or irreversible traps present. The TDS results suggests that non-metallic inclusions indeed serve as irreversible traps along with grain boundaries and dislocations, which serve as reversible traps. Hydrogen permeation measurements were also made on samples prepared from the ¼, ½, and ¾ depths after galvanostatic cathodic charging in an As2O3-containing solution using an applied current density of −10 mA/cm2. Hydrogen gas release was measured using a HYDROSEEL® probe while the sample remained at room temperature (~20°C), providing information regarding the potency of reversible hydrogen traps when subjected to a flux of hydrogen. Only reversible traps can be detected at room temperatures due to their low binding energies. Higher temperatures are required to overcome the larger binding energies associated with irreversible traps. The hydrogen permeation results indicate no significant effect of through-thickness variations in the X60 steel, but the centreline depth of the X70 steel skelp trapped a larger quantity of hydrogen than either of the two quarterline depths, indicating the presence of a distinct problematic trap. The X70 steel skelp was also observed to trap more hydrogen than the X60 steel skelp. The observed hydrogen trapping capacity was linked to the hydrogen embrittlement susceptibility by comparing the uniaxial tensile behaviour of centreline samples with and without hydrogen charging applied as a pre-treatment step. Hydrogen charging was achieved by galvanostatic cathodic polarization at an applied current density of −10 mA/cm2 for 24 h in an NH4SCN-containing solution while simultaneously loading the samples to 85% of the yield strength using a proof ring tensile test cell. An increase in hydrogen embrittlement as a result of pre-charging was confirmed through tensile plots by comparing the area of reduction and failure strain of charged samples to uncharged samples. A decrease in both values was observed in the charged samples indicating a loss in ductility as a result of hydrogen charging. Fracture surfaces were imaged using SEM and inclusions of interest were analyzed for elemental composition using EDS. Inclusions observed along the fracture surfaces include oxysulfides of Ca and Al, oxides of Mg, Al-Ca-Si oxides, and Al2O3-containing inclusions which are likely to be heterogeneous Al-Ca-O inclusions. / Thesis / Master of Applied Science (MASc)

This thesis describes the results of two process system engineering studies: (1) hydrogen pinch analysis; and (2) application of COSMO-SAC (conductor-like screening model – segment activity coefficient) to electrolytes. Part (1) presents an automated spreadsheet method that can quickly help minimize fresh hydrogen consumption and maximize hydrogen recovery and reuse in petroleum refineries and petrochemical complexes. Part (1) has appeared as a featured article on engineering practice in the Chemical Engineering Magazine, volume 115, pp. 56-61, June 2008. We present an automated spreadsheet on our research group website (www.design.che.vt.edu) and describe procedures for using the spreadsheet in this thesis. Part (2) discusses the application of the conductor-like screening model – segment activity coefficient (COSMO-SAC), a liquid-phase activity-coefficient model, to electrolytes. We offer detailed procedure for obtaining sigma profiles for electrolytes. A sigma profile is a molecular-specific probability distribution of the surface-charge density, which enables the application of solvation-thermodynamic models to predict vapor-liquid and solid-liquid equilibria, and other properties. We propose to add an additional term to the exchange energy to account for ion-ion attractive and repulsive forces. We also look at the resulting exchange energy behavior. Although accurate numerical results are not achieved, we are able to produce results that match literature data by adding an adjustment factor. / Master of Science

The successful transition to global clean energy is contingent upon meeting the increasing worldwide energy demand for power while simultaneously curbing greenhouse gas emissions. This study delves into the complexities of transitioning to cleaner energy sources and the challenges posed by utilizing hydrogen and hydrogen/natural gas mixtures as a potential fuel source alternative to traditional carbon-based combustion cycles. By addressing the technical intricacies and conducting thorough testing, researchers aim to enhance our understanding of auto-ignition behavior in different fuel-air mixtures under varying conditions, ultimately contributing to the development of safer and more efficient energy solutions in the pursuit of clean and sustainable power generation. This study outlines the test methodology employed to assess conditions leading to auto-ignition for various fuel-air mixtures operating at different pressures (1 - 30 atm) and temperatures. The testing encompassed 100% H2 and multiple H2/NG blends at stoichiometric conditions. Similar testing was conducted for 100% NG to validate the test procedures and data collection methods referenced in previous literature. Under atmospheric conditions, 0-1 ATM, H2 exhibits a broader flammability range of EQs where ignition is more likely to occur compared to methane. H2's flammability ranges from 4% to 75% molar (volume) fuel concentration, corresponding to an EQ range of 0.137 - 2.57, while methane's flammability limit spans from 5% to 15% molar (volume) or an EQ between 0.53 – 1.58. Previous studies have explored the effect of longer hydrocarbons present in natural gas mixtures, with ethane (C2H6) and propane (C3H8) shown to decrease the ignition temperature (AIT) of natural gas, particularly at elevated pressures. These longer hydrocarbons are inclined to promote ignition in richer conditions, whereas methane tends to ignite more readily in slightly lean conditions. Besides pressure, fuel, and EQ, numerous variables such as chamber volume size, chamber materials, presence of diluents, and other factors can influence the AIT. The results revealed that, at atmospheric pressures, an increase in H2 concentration led to a reduced AIT. However, at 30 atm, a higher presence of H2 increased the AIT. At pressures exceeding 10 atm, an increased equivalence ratio resulted in a decreased AIT for all mixtures, with NG, exhibiting the greatest sensitivity to equivalence ratio variations.

Call number: LD2668 .T4 1965 C532 / Master of Science