An experimental study on the impact of temperature, gasifying agents composition and pressure in the conversion of coal chars to combustible gas products in the context of Underground Coal Gasification

The key controlling factor in the effective energy conversion of coal to combustible gases during the UCG process is the behaviour of the pyrolysed char in the reduction zone of the UCG cavity, which has not been published in available academic literature. This study investigates the impact of the operating parameters during the reduction zone of UCG using a bespoke high pressure high temperature rig which was developed as part of this research work. This rig, operating at temperatures of up to 900 oC and at pressures up to 5.0 MPa, simulates the UCG process including each UCG zone individually for a broad range of underground conditions to a depth of 500 m. Carbon dioxide and steam were used as the primary reductants with char derived from dry steam coal and anthracite sample. Carbon dioxide and steam were injected at a variety of pressures and temperatures, plus at a range of relative H2O/CO2 proportions. The composition of the resulting product gas of both coals was measured and subsequently used to calculate carbon conversion (X), carbon conversion of combustible gases ( ), cold gas efficiency (CGE) and low heating value (LHV) of the product gas. Optimal operating conditions were determined for the dry steam coal and anthracite that produced the best gas composition both at atmospheric and elevated pressure and are unique for each UCG system. A shrinking core model was employed to describe the behaviour of the pyrolised char to determine the activation energy and pre-exponential factor at atmospheric pressure for both coals. The evolution of the volatile matter of both coals and its contribution to the overall UCG performance was also determined. An optimum H2O/CO2 ratio was determined for both coals which enhanced the gasification rate of both coal chars up to the ratio of 2:1, above this ratio the effect saturated for both coals. It was shown that pressure increases the reduction-gasification process of the chars which suggests that there is an optimum operating pressure which produces a peak in carbon conversion, CGE and LHV for the product gas over the conditions tested that differs for each coal. Therefore UCG projects aiming at reaching higher pressures will not achieve an increase in the output, unless there are some new effects occurring above 4.0 MPa. Pressure enhances the gas solid reactions and almost doubles the max carbon conversion ( of combustible gases achieved at elevated pressure compared to that at atmospheric pressure. A shrinking core model was modified to take into account the effect of total pressure to the gasification rate of dry steam coal at 900 oC and pressures ranging from 0.7 to 1.65 MPa. Reaction constants for various pressures at 900 oC were determined for both coal chars. Analysis of data shown that typical UCG operations on low rank coals provides a combustible product gas that relies heavily on releasing the volatile matter from the coal and does not depend on the carbon conversion of char to gas which justifies the high CGE and LHV of the product gas found in the field trials. It was found that carbon conversion X is not significantly affected by the type of coal and that the carbon converted during UCG is between approximately 45% for high rank coals up to 55% for low rank coals. Experimental results were used to calculate the output, size and UCG model of a potential power plant which produced realistic solutions and proves that high rank coals can be suitable for UCG projects. Anthracite can produce almost the same amount of combustible gases as the dry steam coal operating under specific conditions but with a lower CGE and LHV which suggests that anthracite may be found to be more suitable for producing hydrocarbons with UCG than energy

Adhesively Bonded Steel Sandwich Structures for Marine Applications

Sandwich panels, consisting of two facing plates separated by a core of stiffeners, are known to possess high strength and high stiffness to weight ratios. This form of construction is appropriate for structures where the self weight is one of the governing design criteria. This is particularly applicable in cases where the self weight could be reduced while the strength is maintained. The present study deals specifically with the understanding of the performance of adhesively bonded steel corrugated core sandwich structures used for marine applications under realistic loading, namely bending and axial compression. That was done through review on the relevant subjects, theoretical work as well as experimentation. Review on the subjects of adhesion, adhesives, sandwich construction, theory of sandwich construction and the concept of structural connections within the field of sandwich construction are concisely covered from Chapter 1 to Chapter 4, giving in a rather informative way the main outline of each aforementioned subject. As far as the experimental part is concerned, ten models were manufactured especially for the purposes of the present study. More specifically, their components - namely the flat plates and the webs - were joined together by means of a structural adhesive. Therefore, this study demonstrates - and this is clearly shown from Chapter 5 to Chapter 6 - that any failure occurring at this kind of structures is due to buckling either of the flat plate or the web, instead of being due to failure of the adhesive bonding. Two types of bending tests were performed: four point and three point bending tests. Buckling of the webs and any other deformation occurred only adjacent to the points of load application causing some local but not global adhesive and further model damage. Besides, none of the models collapsed. Prediction of the stresses conforms to simple beam theory, although there seem to be some discrepancies between theoretical and experimental values. These could be attributed to imperfections occurring during the manufacture of the models, the material properties from which they are constructed, the installation of the strain gauges, the measuring of the strain gauge values and the important fact that both kinds of bending tests followed either the creep or compression tests. The four point bending tests revealed that the adhesive can influence the performance of the models. In a few words, in terms of real life performance, the strength of the adhesively bonded corrugated core sandwich structures can be seriously affected by the creep of the adhesive. This performance seems to be common for any corrugated core structure irrespective of the combination of face and core geometry. This would seem to preclude use of such structures where significant continuous loading is concerned (for example, heavy weights on deck structure). In contrast to what happens in bending, in compression of this type of structures theory agrees almost perfectly with experiments and this happens mainly because a lot of serious studies have been done in the past by a number of scientists as far as this matter is concerned which results in small deviations to exist. Buckling of the faces and any other deformation occurred only adjacent to the points of load application causing some local but not global adhesive debonding. In conclusion, the model structures designed for the purposes of the present project proved to be stable and strong. The concept of adhesively bonded steel corrugated core sandwich structures specifically designed for marine applications is still new and is worth developing much further by encouraging further research. The findings of the present work have been set all together in Chapter 7 and a number of interesting conclusions accompanied by proposals for future research work appear in Chapter 8

Experimental study on the impact of reactant gas pressure in the conversion of coal char to combustible gas products in the context of Underground Coal Gasification

This paper describes an experimental investigation to determine the impact of pressurised reactor conditions within the reduction zone of a gasification process employing a semi-batch reactor with a bituminous coal. The conditions examined with this bespoke pressurised rig were designed to be representative of an Underground Coal Gasification (UCG) process, at pressures up to 3.0 MPa and temperatures up to 900°C; coal samples were approximately 36g per test. Current published literature suggests that one of the key controlling factors in the conversion and yield within such processes is the behaviour of the pyrolysed coal (char) in the reduction zone of the UCG cavity. This was achieved by using carbon dioxide and steam as the primary reductants with char derived from bituminous coal at a variety of pressure and temperature levels, plus at a range of relative H2O/CO2 proportions. The composition of the resulting product gas was measured and subsequently used to calculate cold gas efficiency and carbon conversion (during 90 minutes at steady state). A shrinking core model was then employed to determine the activation energy and pre-exponential factor under these conditions. The results were then used to extrapolate the contribution of the reduction zone in published research including UCG field trials where discrete analysis of the zones within the gasification cavity was not possible. It was shown that pressure increases the reduction-gasification process of the char in terms of carbon conversion, cold gas efficiency and heating value of the product gas. Under the conditions evaluated herein, optimum gasification conditions for the bituminous coal were determined as 1.65 MPa at H2O/CO2 ratio of 2:1 by mass at 900°C which produced a syngas with a composition of 17.4% CO, 3% CH4, 42.1% H2 and LHV of 7.8 MJ/Nm3

Esponjas como “hoteles vivientes” en cuevas submarinas del Mediterráneo

Although sponges constitute the dominant sessile organisms in marine caves, their functional role as ecosystem engineers has received little attention in this habitat type. In this study the associated macrofauna of the massive/tubular ecosystem-engineering sponges Agelas oroides and Aplysina aerophoba was studied across distinct ecological zones of two eastern Mediterranean caves. Our results revealed that the examined sponges supported a considerable associated macrofauna. A total of 86 associated taxa were found, including species reported for the first time as sponge symbionts and typical cave dwellers. Crustaceans predominated in terms of abundance but polychaetes showed the highest number of taxa. A clear differentiation was observed in the structure of the associated assemblage between the two sponges, attributed not only to the sponge species but also to differences in the surrounding environment. Density, diversity and the trophic structure of the sponge-associated macrofauna did not vary significantly along the horizontal axis of the surveyed caves. These findings suggest that sponges form a quite stable habitat, maintaining their functional role as ecosystem engineers across the studied marine caves and increasing habitat complexity in the impoverished inner dark cave sectors.A pesar de que las esponjas constituyen el grupo sésil dominante en cuevas submarinas, su papel como ingenieros del ecosistema dentro de estos ambientes ha recibido muy poca atención. En el presente trabajo, se ha estudiado la macrofauna asociada a las especies Agelas oroides y Aplysina aerophoba (ambas con una morfología masiva-tubular y consideradas como especies ingenieras del ecosistema) a lo largo de diferentes ambientes situados en dos cuevas marinas del Mediterráneo oriental. Nuestros resultados ponen de manifiesto que las dos especies de esponjas consideradas albergan una abundante fauna asociada. Se encontró un total de 86 taxones diferentes, muchos de los cuales son citados por primera vez como simbiontes de esponjas y habitantes de cuevas submarinas. Aunque los crustáceos fueron el grupo dominante en términos de abundancia, fueron los poliquetos los que presentaron la mayor riqueza taxonómica. Las comunidades asociadas a una y otra esponja presentaron claras diferencias, lo cual se atribuye no solo a diferencias relacionadas con las especies hospedadoras sino también al ambiente circundante. La densidad, diversidad y estructura trófica de la macrofauna asociada a las esponjas no varió significativamente a lo largo del eje horizontal de las cuevas muestreadas. Estos resultados sugieren que las esponjas forman un hábitat bastante estable, manteniendo su papel funcional como ingenieros del ecosistema a lo largo de las cuevas submarinas y, por tanto, incrementando la complejidad del hábitat en los sectores más internos, empobrecidos y oscuros de las cuevas

Sickness Absence in the Private Sector of Greece: Comparing Shipyard Industry and National Insurance Data

Approximately 3% of employees are absent from work due to illness daily in Europe, while in some countries sickness absence exceeds 20 days per year. Based on a limited body of reliable studies, Greek employees in the private sector seem to be absent far less frequently (<5 days/year) compared to most of the industrialized world. The aim of this study was to estimate the levels of sickness absence in the private sector in Greece, using shipyard and national insurance data. Detailed data on absenteeism of employees in a large shipyard company during the period 1999–2006 were utilized. National data on compensated days due to sickness absence concerning all employees (around 2 million) insured by the Social Insurance Institute (IKA, the largest insurance scheme in Greece) were retrieved from the Institute’s annual statistical reports for the period 1987–2006. Sick-leave days per employee and sick-leave rate (%) were calculated, among other indicators. In the shipyard cohort, the employment time loss due to sick leave was 1%. The mean number of sick-leave days per employee in shipyards ranged between 4.6 and 8.7 and sick-leave rate (sickness absenteeism rate) varied among 2% and 3.7%. The corresponding indicators for IKA were estimated between 5 and 6.3 sick-leave days per insured employee (median 5.8), and 2.14–2.72% (median 2.49%), respectively. Short sick-leave spells (<4 days) may account at least for the 25% of the total number of sick-leave days, currently not recorded in national statistics. The level of sickness absence in the private sector in Greece was found to be higher than the suggested by previous reports and international comparative studies, but still remains one of the lowest in the industrialized world. In the 20-years national data, the results also showed a 7-year wave in sickness absence indexes (a decrease during the period 1991–1997 and an increase in 1998–2004) combined with a small yet significant decline as a general trend. These observations deserve detailed monitoring and could only partly be attributed to the compensation and unemployment rates in Greece so other possible reasons should be explored

Online Education for Vaccination Competence Among Health Sciences Students

The EDUVAC project aims to develop and implement a web-based course on educating vaccination competence among health sciences students. In the current study students' feedback and evaluation is assessed which guided the partners' efforts to improve the final course content and learning material that will be available for open access. After completing the web-based course, most of the students (N=103, 75.1%) perceived their vaccination knowledge was up to date and their overall participating experience was "above average or excellent (N=119, 86.9%). While, almost all of the students (N=127, 92.7%) found that the web-based course has benefitted them and their future career. Our findings support that the web-based courses can provide satisfactory learning experience to University students and offer flexibility when needed especially in times that remote education is the only option

Issues with the Specificity of Immunological Reagents for NLRP3: Implications for Age-related Macular Degeneration

Contradictory data have been presented regarding the implication of the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome in age-related macular degeneration (AMD), the leading cause of vision loss in the Western world. Recognizing that antibody specificity may explain this discrepancy and in line with recent National Institutes of Health (NIH) guidelines requiring authentication of key biological resources, the specificity of anti-NLRP3 antibodies was assessed to elucidate whether non-immune RPE cells express NLRP3. Using validated resources, NLRP3 was not detected in human primary or human established RPE cell lines under multiple inflammasome-priming conditions, including purported NLRP3 stimuli in RPE such as DICER1 deletion and Alu RNA transfection. Furthermore, NLRP3 was below detection limits in ex vivo macular RPE from AMD patients, as well as in human induced pluripotent stem cell (hiPSC)-derived RPE from patients with overactive NLRP3 syndrome (Chronic infantile neurologic cutaneous and articulate, CINCA syndrome). Evidence presented in this study provides new data regarding the interpretation of published results reporting NLRP3 expression and upregulation in RPE and addresses the role that this inflammasome plays in AMD pathogenesis