The analysis and prediction of the quantity and composition of household refuse

This thesis describes the development of a simple and accurate method for estimating the quantity and composition of household waste arisings. The method is based on the fundamental tenet that waste arisings can be predicted from information on the demographic and socio-economic characteristics of households, thus reducing the need for the direct measurement of waste arisings to that necessary for the calibration of a prediction model. The aim of the research is twofold: firstly to investigate the generation of waste arisings at the household level, and secondly to devise a method for supplying information on waste arisings to meet the needs of waste collection and disposal authorities, policy makers at both national and European level and the manufacturers of plant and equipment for waste sorting and treatment. The research was carried out in three phases: theoretical, empirical and analytical. In the theoretical phase specific testable hypotheses were formulated concerning the process of waste generation at the household level. The empirical phase of the research involved an initial questionnaire survey of 1277 households to obtain data on their socio-economic characteristics, and the subsequent sorting of waste arisings from each of the households surveyed. The analytical phase was divided between (a) the testing of the research hypotheses by matching each household's waste against its demographic/socioeconomic characteristics (b) the development of statistical models capable of predicting the waste arisings from an individual household and (c) the development of a practical method for obtaining area-based estimates of waste arisings using readily available data from the national census. The latter method was found to represent a substantial improvement over conventional methods of waste estimation in terms of both accuracy and spatial flexibility. The research therefore represents a substantial contribution both to scientific knowledge of the process of household waste generation, and to the practical management of waste arisings

Experimental investigation on the impact of coal fines generation and migration on coal permeability

Measurements of the coal fines production and the impact of these fines on the permeability of two coals from the Bowen Basin, Australia, were performed at different flow conditions (single-phase water or gas, two-phase water and gas) and pressure conditions. The fines collected from each coal samples ranged in size from 1 mu m to 14 mu m. For both coal samples, during the first 50 h, the permeability decreases from 0.005 mD and 0.048 mD by 60.9% and 85%, respectively, followed by gradual decline with fluctuations. By the end of water injection, the permeability drops by 88% and 89%, respectively. This phenomenon is attributed to the counteraction between formation damage (cleats plugging and coal fines settlement) and breakthrough of coal fines from the samples (widened cleats). It was found that coal fines volumetric production is proportional to the third power of flow velocity once the flow paths for coal fines are established. The critical flow velocities of coal fines production for both samples were also obtained. For hydrophobic coal, water-drive-gas two-phase flow introduces abrupt permeability loss due to coal fines generation and migration. Furthermore, pauses (well shut-in) in the experiments cause slight permeability drops. A comparison between the two samples indicates that narrower and less connected cleating system results in more frequent coal fines generation and migration, resulting in significant permeability fluctuations with general decreasing trend. Tortuosity of the cleats can enhance the deterioration in permeability by coal fines behaviours. This study delivers fundamental understandings of coal fines generation and migration during the CSG production process, and useful guidelines are suggested to be implemented in the field to minimize production loss induced by coal fines behaviours

Cross-Linking Amine-Rich Compounds into High Performing Selective CO2 Absorbents

Amine-based absorbents play a central role in CO2 sequestration and utilization. Amines react selectively with CO2, but a drawback is the unproductive weight of solvent or support in the absorbent. Efforts have focused on metal organic frameworks (MOFs) reaching extremely high CO2 capacity, but limited selectivity to N2 and CH4, and decreased uptake at higher temperatures. A desirable system would have selectivity (cf. amine) and high capacity (cf. MOF), but also increased adsorption at higher temperatures. Here, we demonstrate a proof-of-concept where polyethyleneimine (PEI) is converted to a high capacity and highly selective CO2 absorbent using buckminsterfullerene (C60) as a cross-linker. PEI-C60 (CO2 absorption of 0.14 g/g at 0.1 bar/90°C) is compared to one of the best MOFs, Mg-MOF-74 (0.06 g/g at 0.1 bar/90°C), and does not absorb any measurable amount of CH4 at 50 bar. Thus, PEI-C60 can perform better than MOFs in the sweetening of natural gas

Predictors of complications in gynaecological oncological surgery: a prospective multicentre study (UKGOSOC-UK gynaecological oncology surgical outcomes and complications)

Background: There are limited data on surgical outcomes in gynaecological oncology. We report on predictors of complications in a multicentre prospective study. / Methods: Data on surgical procedures and resulting complications were contemporaneously recorded on consented patients in 10 participating UK gynaecological cancer centres. Patients were sent follow-up letters to capture any further complications. Post-operative (Post-op) complications were graded (I–V) in increasing severity using the Clavien-Dindo system. Grade I complications were excluded from the analysis. Univariable and multivariable regression was used to identify predictors of complications using all surgery for intra-operative (Intra-op) and only those with both hospital and patient-reported data for Post-op complications. / Results: Prospective data were available on 2948 major operations undertaken between April 2010 and February 2012. Median age was 62 years, with 35% obese and 20.4% ASA grade ⩾3. Consultant gynaecological oncologists performed 74.3% of operations. Intra-op complications were reported in 139 of 2948 and Grade II–V Post-op complications in 379 of 1462 surgeries. The predictors of risk were different for Intra-op and Post-op complications. For Intra-op complications, previous abdominal surgery, metabolic/endocrine disorders (excluding diabetes), surgical complexity and final diagnosis were significant in univariable and multivariable regression (P<0.05), with diabetes only in multivariable regression (P=0.006). For Post-op complications, age, comorbidity status, diabetes, surgical approach, duration of surgery, and final diagnosis were significant in both univariable and multivariable regression (P<0.05). / Conclusions: This multicentre prospective audit benchmarks the considerable morbidity associated with gynaecological oncology surgery. There are significant patient and surgical factors that influence this risk

Modeling and cost analysis of helium recovery using combined-membrane process configurations

This study used process simulations to evaluate the potential of three configurations of cascade membrane process flowsheets to recovery helium from a stream containing 1% helium in 98.3% nitrogen and 0.7% methane, which represents a typical vent stream from nitrogen rejection units in some liquefied natural gas (LNG) plants. We considered three-stage cascade membrane process flowsheets and investigated the placement within these stages of three types of commercial membranes - Hyflon (R) AD60X, polyimide (PI), and polysulfone (PS). Flowsheet simulations conducted in Aspen HYSYS with a custom membrane unit and the simulation data used in techno-economic analyses to evaluate recovery of helium to upgraded helium with at least 90 mol. % He and grade-A with 99 mol % He purity. To produce the 90 mol % He stream at a 95% He recovery, we found that a configuration with the high permeability-moderate selectivity AD60X membrane in the first and second membrane stages and the moderate selectivity-moderate permeability PI membrane in the third membrane stage lead to the lowest helium breakeven production cost of US.$149.89/MSCF. To produce the 99 mol$ 187.81/MSCF for grade-A helium at an 82% He recovery. We included a sensitivity analysis to understand how the He recovery rate, cost of electricity, and membrane price may effect the breakeven production cost

Emission characteristics of polymer additive mixed diesel-sunflower biodiesel fuel

Combustion of fossil fuels has a significant share in producing harmful emissions in the global emission context. With a threat of fossil fuel crisis and the necessity of reducing emission from diesel engine combustion system, biodiesel is considered as one of the key environmentally-friendly diesel fuel alternatives. In this study, sunflower biodiesel has been considered as a key ingredient to infuse waste plastic (polystyrene, PS) as another cleaner source of hydrocarbon fuel in the diesel engines. Polystyrene was infused (5% w/v) into sunflower biodiesel to produce a blend of diesel-biodiesel-polymer (DBP) fuel. The emission characteristics of the diesel, diesel–biodiesel (binary blend) and diesel-biodiesel-polymer (ternary blend) were compared in an unmodified diesel engine. The results showed that the emission compositions of the DBP were comparable to those of diesel which effectively reduced the NOx emission, as compared to diesel-biodiesel blend. In addition, the brake specific fuel consumption (BSFC) and CO emission were reduced in DBP, as compared to biodiesel and diesel fuels. Based on these results, it can be concluded that the polymer blended fuels could be potentially used as another emission reducing fuel source in an unmodified diesel engine. The utilisation of waste polymers in biodiesel production could help find an alternative use for non-recyclable plastics, while also contributing to cleaner emission

High-performance cobalt-tungsten-boron catalyst supported on Ni foam for hydrogen generation from alkaline sodium borohydride solution

Low cost and catalytically effective transition metal catalysts are highly wanted in developing on-demand hydrogen generation system for practical onboard application. By using a modified electroless plating method, we have prepared a robust Co–W–B amorphous catalyst supported on Ni foam (Co–W–B/Ni foam catalyst) that is highly effective for catalyzing hydrogen generation from alkaline NaBH4 solution. It was found that the plating times, calcination temperature, NaBH4 and NaOH concentrations all exert considerable influence on the catalytic effectiveness of Co–W–B/Ni foam catalyst towards the hydrolysis reaction of NaBH4. Via optimizing these preparation and reaction conditions, a hydrogen generation rate of 15 L/min g (Co–W–B) has been achieved, which is comparable to the highest level of noble metal catalyst. In consistent with the observed pronounced catalytic activity, the activation energy of the hydrolysis reaction using Co–W–B/Ni foam catalyst was determined to be only 29 kJ/mol. Based on the phase analysis and structural characterization results, the mechanism underlying the observed dependence of catalytic effectiveness on the calcination temperature was discussed

Electrode, Electrolyte, and Membrane Materials for Electrochemical CO<inf>2</inf> Capture

Publication status: PublishedFunder: UQ Dow Centre for Sustainable Engineering InnovationAbstractOne of the many possible ways to capture carbon dioxide (CO2) is through electrochemical means. This is an emerging approach with various merits. It is energy efficient, utilizes renewable energy, operates under ambient conditions, provides ease for control of reaction rates, and is scalable. Additionally, it can be integrated as a plug‐and‐play module at various scales, including large industrial sources or at small scale, e.g., on vehicles, and can easily combine CO2 capture, storage, and utilization into value‐added chemicals. Various “proof‐of‐concept” electrochemical CO2 capture approaches have been demonstrated in the recent past. These are made possible with electro‐active materials that capture, separate, and concentrate CO2 in the form of electrodes, electrolytes, and membranes in devices. Herein, these materials and their working mechanisms are identified and reviewed in various electrochemical CO2 capture devices where they are utilized. Also, the current challenges and future research directions with the identified electrodes, electrolytes, and membranes are summarized to give a rational understanding and guidance for selecting and designing materials for use in electrochemical CO2 capture devices.</jats:p

Kinetic-and thermodynamic-based improvements of lithium borohydride incorporated into activated carbon

LiBH4 was incorporated into an activated carbon (AC) scaffold using a chemical impregnation method. Confinement of LiBH4 within the carbon nanopores was found to significantly improve both the hydrogen sorption kinetics and thermodynamics, compared to the bulk hydride. The LiBH4/AC sample starts to release hydrogen from just 220 °C, which is 150 °C lower than the onset dehydrogenation temperature of bulk LiBH4. The dehydrogenation rate of the LiBH4/AC sample was one order of magnitude faster than that of bulk LiBH4. The temperature and hydrogen pressure conditions required for restoring the hydride were also significantly reduced when LiBH4 was incorporated into AC. Preliminary study showed that the dissociation hydrogen pressure of LiBH4 could be enhanced by around one order of magnitude upon incorporating the hydride into AC. X-ray diffraction, Fourier transform infrared spectroscopy and nitrogen adsorption analyses were used to confirm the nanostructure of LiBH4 in the AC scaffold

Non-invasive current collectors for improved current-density distribution during CO2 electrolysis on super-hydrophobic electrodes

Abstract Electrochemical reduction of CO2 presents an attractive way to store renewable energy in chemical bonds in a potentially carbon-neutral way. However, current electrolyzers suffer from intrinsic problems, like flooding and salt accumulation, that must be overcome to industrialize the technology. To resolve flooding and salt precipitation issues, researchers have used ultra-hydrophobic electrodes based on either polytetrafluoroethylene (PTFE) gas-diffusion layers (GDL’s), or carbon-based GDL’s with added PTFE. While the PTFE backbone is highly-resistant to flooding, the non-conductive nature of PTFE means that without additional current collection the catalyst layer itself is responsible for electron-dispersion, which penalizes system efficiency and stability. In this work, we present operando results that illustrate the poor current/potential distribution in thin catalyst layers (~50 nm) deposited onto PTFE GDL’s. We then compare the effects of thicker catalyst layers (~500 nm) and a newly developed non-interfering current collector (NICC). The NICC can maintain even current distribution with 10-fold thinner catalyst layers while improving stability towards ethylene (≥ 30%) by approximately two-fold