This thesis examines the prospect of structure H (sH) hydrate to be exploited for methane storage. The methane content in the hydrate, hydrate kinetics and conversion rates are areas of particular importance. Experiments and theory are employed at the macroscopic and molecular levels to study the relevant phenomena. sH hydrate was successfully synthesized from ice particles with full conversion achieved within a day when thermal ramping above the ice melting point was applied. It was found that a polar guest (tert-butyl methyl ether / TBME) wets ice more extensively compared to two hydrophobic guests (neo-hexane / NH and methyl-cyclohexane / MCH). TBME also has much higher solubility in water. Consequently, the system with TBME was found to exhibit the highest initial hydrate formation rate from ice particles or in water in a well stirred vessel. However, the rate with the hydrophobic guests was the fastest when the temperature exceeded the ice point. Thus, the applied temperature ramping compensated the slow kinetics below the ice point for the hydrophobic guests and allowed faster overall conversion than the polar guest. Structure, cage occupancy, composition and methane content in the hydrate were also determined by employing different techniques and the results were found to be consistent. It was found that the methane content in structure H hydrate with TBME was the smallest (103-125 v/v) whereas that with NH was 130-139 (v/v) and that with MCH was 132-142 (v/v). The methane content in structure II hydrate by using propane (C₃H₈) and tetrahydrofuran (THF) as the large guest molecule were also estimated. Optimal methane content was found at approximately 100 (v/v) for both C₃H₈ and THF systems with the large guest concentrations at 1% for C₃H₈ (10°C) and 1% for THF (room temperature). The gas content is of course lower than that for structure I hydrate (170 v/v) but one should consider the fact that the hydrate formation conditions are much lower (less than 1 MPa). Finally, MD simulations revealed for the first time the formation of defects in the cavities for the TBME/methane/water (sH hydrate) system which may affect hydrate stability and kinetics.

[Truncated abstract] The ‘elemental sulphur’ deposition problem is a fairly recent phenomenon for gas transmission pipelines. Although known for a number of decades to cause plugging in reservoir wellhead facilities, it is since about 1990 that ‘elemental sulphur’ deposition has openly been acknowledged as a problem in natural gas pipelines and other facilities downstream of gas processing plants. Within the past ten years this formation / deposition process has progressively been more widely observed. The increasing trend to have transmission pipeline systems operating at higher pressures is a significant contributing factor in the formation of “elemental sulphur”. This research project has been able to identify the principles and mechanisms associated with the formation and deposition ‘sulphur vapour map’ concept, that only sub ppm levels of sulphur vapour within the gas stream is required to initiate the “elemental sulphur” formation / deposition process. The ‘sulphur vapour map’ can be used in predicting the degree of sulphur vapour desublimation that will occur for given pipeline operating conditions of pressure, temperature and gas composition. This, in turn, will assist in the minimization of the deposition process through the ability to make simple, yet appropriate, modifications to the design of the required pipeline pressure regulation stage. A significant number of other potential contributing factors to this pipeline particle formation and deposition process have also been identified through this research work. From these findings a number of additional recommendations have been made that will assist pipeline operators in minimizing the impact of this deposition problem. These recommendations are based on the operation of the pipeline, and particularly the control of the entry of liquids and other contaminants into the pipeline system. Recommendations for further research into this complex problem are also made.

Utilisation of natural gas (mainly methane, CH[subscript]4), a clean and abundant resource, is of great importance. Conventional method, steam reforming, though still dominant, requires a considerately high capital investment and an intensive energy input. Reforming natural gas by partial oxidation, potentially one of the most attractive alternatives, has been investigated vigorously for decades, mainly focusing on looking for suitable catalyst and understanding of the mechanisms of methane partial oxidation. This work focuses on the feasibility of methane partial oxidation reforming from gas phase reaction under fuel-rich conditions.Firstly, a detailed thermodynamic analysis has been conducted, which covers a broad range of operation conditions of temperature up to 2073 K, pressure up to 100 atm and initial O(subscript)2/CH(subscript)4 ratio of 0 to 2.5. It has been found that high syn-gas (H(subscript)2 and CO) yields can be achieved when the temperature is above 1073 K and the initial O(subscript)2/CH(subscript)4 ratio close to 0.5. High pressure is not favoured. However, high temperatures can suppress the effect of high pressures.Carbon deposition, a crucially important factor in methane partial oxidation, is mainly examined by means of thermodynamic analysis. Solid carbon was identified the major carbon deposition form, which could severely happen if the initial O(subscript)2/CH(subscript)4 ratio is less than 0.5. This feature was also indirectly proven during the experimental tests.Secondly, a series of CHEMKIN simulations were performed using various CH(subscript)4 oxidation reaction mechanisms. The general trend of the CH(subscript)4 partial oxidation reforming was revealed by simulations using the GRI, NIST and Konnov mechanisms. A new concept characterising CH(subscript)4 partial oxidation was conceived. i.e., a fast oxidation zone and a slow conversion ++ / zone, the reaction is under chemical control that requests high operating temperatures, and the reaction can be accelerated by using relatively high initial 0(subscript)2/CH(subscript)4 ratios.Experimental tests were performed to verify the findings obtained in thermodynamic and kinetic studies, and to identify appropriate reaction schemes for further analysis. Prediction from the NIST mechanisms has shown to be in good agreement with experimental observation when the temperature is less than 1273 K. For higher temperatures the NIST under-predicts the H(subscript)2 yield caused by the lack of carbon formation mechanisms. Two other mechanisms (Konnov and GRI) predicted similar trends but the reaction predicted commenced earlier. Therefore, the NIST was identified to be the best.NO(subscript)x catalytic effect on CH4 oxidation at fuel-rich conditions was confirmed experimentally. However, this effect only exists where the oxygen is available. Therefore, employing NO(subscript)x cannot help the CH(subscript)4 partial oxidation in the second reaction zone. Solely relying on NO(subscript)x to speed up the process or lower the operating temperature is not possible. However, employing NO(subscript)x to initiate the reaction at lower temperatures is viable. The possibility of taking the advantage of NOx catalytic effect for direct synthesis of CH3OH (methanol) has been shown feasible and, more attractively, the operating temperatures required are much lower than that for syn-gas production.Among three reaction schemes, i.e., the Glarborg, Bromly and Dagaut, which are able to account for the NO(subscript)x catalytic effect, the Glarborg mechanism proved to be the best in reproducing experimental measurements for syn-gas production tests. However, none available mechanisms can predict similar magnitude of the direct synthesis of CH(subscript)3OH. To understand the mechanisms ++ / of NO(subscript)x catalytic effect, a reaction scheme, Partial Oxidation Mechanisms (POM), has been composed successfully adding five additional reactions into the NIST. The POM can reveal the major catalytic reaction pathways and it is suitable for CH(subscript)4 partial oxidations both with and without NO(subscript)x addition.Finally, a series of simulations were conducted to conservatively estimate the feasibility of CH(subscript)4 partial oxidation using POM. High syn-gas yield is achievable within a reasonable residence time using adiabatic reactor. The variables significantly affecting the syn-gas yield, are preheating temperature, operating pressure, inert dilution, initial ratio of O(subscript)2/CH(subscript)4 and residence time. If NO(subscript)x is used as a catalyst, the preheating temperature can be further reduced.

Thesis (Ph.D.)--University of Tulsa, 1985. / Bibliography: leaves 186-192.

Thesis (M.S.)--Ohio University, August, 1999. / Title from PDF t.p.

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains ix, 100 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references (p. 72-73).

Thesis (M.S.)--Marshall University, 2008. / Title from document title page. Includes abstract. Document formatted into pages: contains ix, 94 p. : ill. Includes bibliographical references (p. 90-91).

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (v.85-89).

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (p. 215-232).

Thesis (Ph. D.)--Oregon State University, 1995. / System requirements for computer disk: IBM-compatible PC. Typescript (photocopy). Includes plates in pocket. Includes bibliographical references. Also available on the World Wide Web.