Browsing by Author "White, Graeme"

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Chemical looping combustion for carbon capture
(Heriot-Watt University, 2016-04) Porrazzo, Rosario; Ocone, Raffaella; White, Graeme
Among the well-known state-of-art technologies for CO2 capture, Chemical Looping Combustion (CLC) stands out for its potential to capture with high efficiency the CO2 from a fuel power plant for electricity generation. CLC involves combustion of carbonaceous fuel such as coal-derived syngas or natural gas via a red-ox chemical reaction with a solid oxygen carrier circulating between two fluidised beds, air and fuel reactor, working at different hydrodynamic regimes. Avoided NOx emissions, high CO2 capture efficiency, low CO2 capture energy penalties and high plant thermal efficiency are the key concepts making worthy the investigation of the CLC technology. The main issue about the CLC technology might concern the cost of the solid metal oxides and therefore the impact of the total solid inventory, solid make-up and lifetime of the solid particles on the cost of the electricity generated. A natural gas fired power plant embedding a CLC unit is presented in this work. Macro scale models of fluidised beds (i.e. derived applying macroscopic equations) are developed and implemented in Aspen Plus software. Kinetic and hydrodynamic phenomena, as well as different operating conditions, are taken into account to evaluate their effect on the total solid inventory required to get full fuel conversion. Furthermore, a 2D micro scale model of the fuel reactor (i.e. derived applying partial differential equations), making use of a CFD code, is also developed. The results, in terms of the effect of the different kinetic and hydrodynamic conditions on the outlet gas conversion, are compared with the results using the macro-scale model implemented in Aspen Plus. Based on the micro scale (CFD) outcomes, the macro scale model is enhanced to capture the main physics influencing the performance of the fuel reactor. Thus, the improved macro scale model is embedded into different power plant configurations and mass and energy balances are solved simultaneously. Thermal efficiency evaluations for the different plant arrangements are carried out. A detailed economic evaluation of the CLC power plant is undertaken by varying two relevant parameters: fuel price and lifetime of the solid particles. The effect of the aforementioned parameters on the Levelised Cost Of Electricity (LCOE) is investigated and the resulting outcomes are critically discussed.
The effect of sea induced motion on offshore process equipment
(Department of Chemical and Process Engineering, 1990-05) White, Graeme
Abstract unavailable refer to PDF
The effect of sea induced motion on offshore process equipment
(Heriot-Watt University, 1990-05) White, Graeme; Waldie, Professor Brian
The performance of offshore process equipment on floating production platforms may be reduced through imposed sea motion. Fluid sloshing inside primary separators and non-segregated storage tanks may lead to oil/water mixing. The aim of previous work into sloshing has been to prevent damage to LNG tankers and increase the stability of space rockets. Work into oil/water sloshing appears limited. A computer controlled motion simulator was developed to conduct experiments with two rectangular vessels filled with air, refined oil and water. Two single sinusoidal forcing motions were applied, pitch and surge at various amplitudes and periods. Additional experiments were conducted with combined forcing motions pitch/roll and pitch/surge. Air/water interface profiles were measured and analysed using a computer based data logging and processing system. Air/oil and oil/water profiles were recorded using high speed video equipment. Also studied were the effect of baffles in reducing interface amplitude and the effect of forcing on oil/water transfer. A linear theory was derived to predict natural frequencies of three fluid systems and a numerical model was developed to predict near resonant behaviour. Air/water experiments and numerical model showed a coupling of natural and forcing frequencies in the free surface frequency spectrum. Favourable comparisons were also seen between the numerical model and oil/water experiments. Additional experiments indicated that oil/water mixing is promoted by resonant forcing in an unbaffled vessel. The presence of baffles reduces interfacial breakup and hence reduces oil content of water.