This study investigates the performance of a hybrid turboexpander and fuel cell (HTEFC) system for power recovery at natural gas pressure reduction stations. Simulations were created to predict the performance of various system configurations. Natural gas is transported at high pressure across large distances. The pressure of the natural gas must be reduced before it is delivered to the consumer. Natural gas pressure reduction is typically achieved using pressure reduction throttling valves. In a limited number of cases pressure reduction is achieved using a turboexpander. This method has the added bonus of power generation. There is a considerable temperature drop associated with the turboexpander process. Preheating is required in many cases to avoid undesirable effects of a low outlet temperature. This preheating is typically done using gas fired boilers. The hybrid system developed by Enbridge and Fuel Cell Energy is a new approach to this problem. In this system a Molten Carbonate Fuel Cell (MCFC) running on natural gas is used in conjunction with the turbine to preheat the gas and provide additional low emission electrical power Various system configurations were simulated and factors affecting the overall performance of the systems were investigated. Power outputs, fuel requirements and efficiencies of various system configurations were found using typical gas flow variation data. The simulation was performed using input data from the current city gate pressure reduction station operated by Utilities Kingston. Using the data provided by Utilities Kingston the performance of various potential HTEFC system configurations were compared. This thesis illustrates the benefits of using this type of analysis in a feasibility study of future HTEFC systems for power recovery at natural gas pressure reduction stations. Improvements could be made to the accuracy of the simulation results by increasing the complexity of the individual component models. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-11-12 18:35:30.266

A critical re-examination of the liberal peace is conducted to explore the ways in which certain ideas around peace have come to dominate and to be regarded as “common sense”. The foundation of my critique comes in the personalisation of peacebuilding through the stories of people who are the intended beneficiaries of its actions. This thesis seeks to open up and challenge the current measures of success and the location of power by introducing voices and experiences of Mende people located in the Southern and Eastern provinces of Sierra Leone. I have attempted to open up a reflexive space where simple questions can be re-examined and the location of recovery can be seen as a space influenced, shaped and performed in the context of diverse influences. I draw on my personal experience living in Bo, Sierra Leone for two months in 2014 and local level actors' subjective reflections on individual and communal notions of recovery, post-conflict. My findings are reflected in “building blocks” that uncover a partial story of personal perspectives on recovery. The story suggests a de-centred and complex “local” within the existing context and realigns the understanding of subject and agency within peacebuilding. This collection of experiences, stories and encounters reshapes the notion of peace as an everyday activity with the aim of improving well-being on a personal level. It is also a part of the peacebuilding process that exists outside of the traditional organisational lens. My main contribution has been in allowing alternative space(s) of peacebuilding and peace-shaping to have a platform that is not restricted by the confined epistemic “expert” community toward an understanding of “progress” as an experiential and subjective process of recovery. This approach sought to challenge the current site of legitimacy, power and knowledge, and in order to achieve this aim I drew on a new methodological toolkit and the absorption of key concepts from other disciplines such as managerialism and the sociological concept of the “stranger”. My research offers an opportunity to observe and utilise information sourced from the creativity and spontaneity of the everyday lived experiences of Sierra Leoneans and ordinary phenomena connected with this.

Power dispersion within oil injected screw air compressors : The PhD-work shows the power dispersion within the oil- and air circuits of oil injected screw air compressors for the working pressures (Pd), where Pd has been tested for Pd ≤ 8,5 bar (a) and Pd ≤14,0 bar(a) respectively. The executed test runs with mineral oil have further confirmed the suppliers quoted performance data within stated tolerances. For comparison of the compressor performance with type of lubricant, the performance tests have been repeated with the four most common types of lubricants, which today are commercialised for screw air compressors. The selected lubricants hold the same cinematic viscosity (ISO VG 46), but the lubricants diverge in question of solubility of air and in formation of air bubbles during the compression cycle. These phenomenas confirm deviations in prevailing viscosity in the oil film and demonstrate that the performance data vary slightly with selected type of lubricant. The tests have proven that the air, which dissolve in the lubricant during the compression cycle will not degas during the resting period in the air/oil receiver, nor will the miniscule air bubbles degas due to their low ascending speed. This means that the content of dissolved air and air bubbles in the oil in the receiver becomes the most elevated within the system and where the temperature is the highest within the compressor cycle. Further is the resting period of the oil in the receiver extreme long in relation to the over all operating cycle of the oil. The conclusion is that the destruction (oxidation) of the oil is taking place in the oil/air receiver and nowhere else within the system. To counteract the oxidation and other destructive processes in the oil circuit « additives » are introduced in the oil. So are e.g. anti-oxide additives reducing the formation of peroxides and are by this reducing the oxidation velocity of the oil until the additives have been consumed. These additives are reducing the oxidation velocity of the lubricants, but will as well, due to the increased polarity caused by the additives, increase the content of dissolved water in the oil. However, this increased content of dissolved water is (strongly) reducing life of the roller bearings. The measured quantities of dissolved water in the lubricants (after the executed tests) have been compared with achieved bearing life from tests executed by others. The PhD work is finally summarizing that the only method to strongly reduce the destruction of the lubricant is to immediately separate off the oil from the compressed air at exit of the compressor. In addition, the today's « dumped » power in the oil cooler can be recovered to increase the available pneumatic power by some 25-30%. Assumingly, this increase in working temperature of the pneumatic air will, in addition increase the efficiency in applied pneumatic tools.