Formation of a mineral layer during coke dissolution into liquid iron and its influence on the kinetics of coke dissolution rate

The formation and development of the mineral layer that forms between coke and liquid iron during carbon dissolution has been characterised. Coke particles (-2mm, +0.5mm) were added to the top surface of an iron 2 mass% C melt at representative ironmaking temperatures, for periods of time between 2 minutes and 120 minutes, before being quenched. The quenched samples were then sectioned and the solidified coke-melt interfacial region analysed in the SEM. Analysis showed that a mineral layer was present at the interface at all experimental temperatures (1450-1550oC) from 2 minutes and persisted beyond 120 minutes. The mineral layer was found to be composed of calcium aluminate phases, with the proportions of these phases dictating its morphology. Further, changes observed in the rate of carbon dissolution from the coke were related to the composition and morphology of the mineral layer. The effect of this mineral layer on the rate of carbon dissolution has been interpreted as a change in the reaction control mechanism

The effect of sulfur concentration in liquid iron on mineral layer formation during coke dissolution

The effects of sulfur concentration in liquid iron on mineral layer development between coke and iron as coke dissolves in a 2 mass % carbon-iron liquid have been investigated at 1500°C. Initial sulfur in iron concentrations used ranged from 0.006 to 0.049 mass %. Key findings include that the two stage dissolution behavior exhibited in the carbon transfer from coke to iron as reported in a previous study by the authors, at low initial sulfur in iron contents, was also apparent at the higher values used in this study. This two stage behavior was attributed to a change in the mineral layer density, as a result of changes in mineral morphology at the interface. In addition to confirming the two stage behavior of the carbon transfer kinetics at the higher sulfur concentration in iron levels, it was also found that after a period of time a solid calcium sulfide layer formed on the mineral layer. The sulfide layer formed after approximately 40 minutes and the proportion of sulfide in the mineral layer increased with increased experimental time and initial sulfur concentration in iron. It was usually found at the iron side of the mineral layer and associated with calcium enriched calcium aluminates. Thermodynamic analysis of this layer confirmed that the sulfide is stabilized as the mineral layer is enriched by calcium

Epidemiological factors associated with human cystic echinococcosis: A semi-structured questionnaire from a large population-based ultrasound cross-sectional study in eastern Europe and Turkey

Background: Cystic echinococcosis (CE) is a neglected parasitic zoonosis prioritized by the WHO for control. Several studies have investigated potential risk factors for CE through questionnaires, mostly carried out on small samples, providing contrasting results. We present the analysis of risk factor questionnaires administered to participants to a large CE prevalence study conducted in Bulgaria, Romania and Turkey. Methods: A semi-structured questionnaire was administered to 24,687 people from rural Bulgaria, Romania and Turkey. CE cases were defined as individuals with abdominal CE cysts detected by ultrasound. Variables associated with CE at P < 0.20 in bivariate analysis were included into a multivariable logistic model, with a random effect to account for clustering at village level. Adjusted odds ratios (AOR) with 95% CI were used to describe the strength of associations. Data were weighted to reflect the relative distribution of the rural population in the study area by country, age group and sex. Results: Valid records from 22,027 people were analyzed. According to the main occupation in the past 20 years, "housewife" (AOR: 3.11; 95% CI: 1.51-6.41) and "retired" (AOR: 2.88; 95% CI: 1.09-7.65) showed significantly higher odds of being infected compared to non-agricultural workers. "Having relatives with CE" (AOR: 4.18; 95% CI: 1.77-9.88) was also associated with higher odds of infection. Interestingly, dog-related and food/water-related factors were not associated with infection. Conclusions: Our results point toward infection being acquired in a "domestic" rural environment and support the view that CE should be considered more a "soil-transmitted" than a "food-borne" infection. This result helps delineating the dynamics of infection transmission and has practical implications in the design of specific studies to shed light on actual sources of infection and inform control campaigns