1,720,968 research outputs found
Enrichment of Silica Sand Ore by Cyclojet Flotation Cell
No full textCyclojet flotation is an alternative technique of jet flotation.
It essentially has a mechanism for bubble formation with pulp
jet spouting from the apex of hydrocyclone. The size of the bubbles
formed with pulp jet in the cyclojet cell is very small, and
the quantity of bubbles produced also limits its potential to produce
high bubble-particle collision. This is particularly efficient in
beneficiation of fine-grained ores. In this study, the performance
of the cyclojet flotation cell was tested for removing iron-oxides
from silica sand ore. Whether it can be used as an alternative to
conventional mechanical cells was studied. The findings obtained
from the cyclojet cell were compared with findings obtained from
the conventional cell. It was seen that the cyclojet cell produced
slightly better results than the conventional cell. Under the best
conditions, while the cyclojet cell reduced the iron-oxide content
in silica sand from 0.41% to 0.08%, the conventional cell reduced
it to 0.10%. While iron removal efficiency was 80.49% for the
cyclojet flotation, it was calculated as 75.61% for the conventional
cell. These findings showed that cyclojet flotation can be used as
an alternative method to conventional flotation for the removal of
iron oxides from silica sand
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Comparison of Efficiencies of Microwave and Conventional Electric Ovens in the Drying of Slime-Coal Agglomerates
No full textCurrently nearly 6 million tonnes of bituminous coal are produced in Turkey and more than 0.3 million tonnes of slime coal are discarded from the coal-washing plants. Slime coal is a low-calorie fuel containing clay and other minerals and high levels of moisture. The filter cake sample used for the study was obtained from a hydrocyclone overflow. The moisture content of the disc-filtered bituminous coal was 26% and its average particle size was similar to 30 microns. The slime-coal filter cake sample was agglomerated in 2 cm diameter material before the drying experiments. The agglomerates were dried separately in both microwave and conventional ovens. After the drying process, the efficiency of each oven was determined. The surface temperatures and compressive strengths of the agglomerates dried in both types of oven were compared. In the microwave oven, micro- and macrocracks appeared on the agglomerates causing them to dry faster. In that manner, the drying efficiency of the microwave was found to be higher. As the microwave energy heated the agglomerate selectively, the surface temperature was found to be lower. However, the quick-drying process caused a decrease in the strength of agglomerates
Effect of Temperature on Coal Flotation with Waste Vegetable Oil as Collector
No full textIn this study, the effect of pulp temperature on coal flotation was investigated. Waste vegetable oil was used as collector. Experiments were carried out at different temperatures (5, 25, 50, and 75 degrees C) and the pros and cons of each temperature for flotation performance were revealed. While flotation performance was lower in higher pulp temperatures (50 and 75 degrees C), flotation performance was found higher in lower pulp temperatures (5 and 25 degrees C). Highest combustible recovery values were obtained at 25 degrees C pulp temperature, and the lowest ash product was obtained at 75 degrees C. However, the lowest combustible recovery value was obtained in flotation at 75 degrees C
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Application of the modified water-only cyclone for cleaning fine coals in a Turkish washery, and comparison of its performance results with those of spiral and flotation
No full textWater-only cyclone (WOC) is an autogenous medium cyclone which performs a gravity separation using water as a separating fluid. Modified water-only cyclones (MWOC) are presently being used for fine coal cleaning in only two washeries in Turkey. In this study, MWOC was designed, installed via local facilities, and then implemented for the treatment of fine coal. The effects of the major parameters of MWOC, such as cyclone diameter, vortex finder diameter and apex diameter, on washing performance were investigated in detail. Then, the results obtained through the MWOC under optimum conditions were compared with those obtained through spiral and flotation. The tests show that the MWOC produced clean coal equal in quality to that produced by the spiral and flotation machine. However, the clean coal yield of the MWOC is quite a bit lower than that of the spiral and flotation machine, and the reject contains a significant amount of combustible matter. In summary, it was concluded that the MWOC can be used in washeries for pre-enrichment due to its simple structure, easy-control features and lower operational costs. (C) 2012 Elsevier B.V. All rights reserved
The production of ultra-clean coal from Zonguldak bituminous coal by chemical leaching
No full textFrom run-of-mine coal with an average ash of 50% being produced at Zonguldak coal basin, clean coal with 7% ash can be produced through physical enrichment methods such as jig and heavy media. However, for the production of coal with an ash content of lower than 7%, it is required for the coal to be first ground and then subjected to chemical leaching operation. In this study, chemical leaching tests were performed with aqueous HF, HCL, HNO3, and citric acid (CA) in order to produce ultra-clean coal (UCC) from Zonguldak bituminous coal. The effects of type of chemical, grain size, temperature, and leaching time in the leaching process were studied. It was observed that UCC with 0.82% ash could be produced from sample coal with 8.84% ash as the result of leaching operation with aqueous HF
Optimization of Some Parameters in a Modified Water-Only Cyclone for Metallurgical Coal Production from High-Ash Fine Coking Coals
No full textCoking coal with generally 11% or lower ash content is termed as metallurgical coal and is used in the steel industry after the coking process. In Turkey, generally spirals and flotation machines are used for the production of metallurgical coal from high-ash fine coals. According to plant data, these devices are capable of producing clean coal with an ash content of 7%-15% from raw coal with 40%-60% ash content. This study aimed to produce metallurgical coal from high-ash coal using a modified water-only cyclone as this method is simple and easy to control. Firstly, the conventional water-only cyclone was modified, then some important operating parameters such as cyclone inclination, inlet pressure, and solids concentration were optimized. Following the optimization procedure, it was found that clean coal of metallurgical quality with 11% or lower ash content can be produced using a modified water-only cyclone
A new process for the production of medium quality fuels from coal washing plant coarse tailings
No full textTurkey's proven bituminous coal reserve is very low, and it is about 1.3 billion tons. The annual bituminous coal production is 2 million tons, and the annual import amount is 30 million tons. Turkey is a foreign-dependent country in its bituminous coal requirement. In this respect, the highest recycling of coarse and fine plant tailings is important in respect of the efficient use of limited natural resources. In this study, a novel process was developed for medium quality fuel production from coarse plant tailings. By the developed process, from coarse plant tailings with an ash content of 78.21%, medium quality fuel was produced which has ash content between 29.20 and 44.38% and which has economic value in the current market. The upper calorific values of these fuels change between 5620 and 4350 kcal/ kg. The developed process basically includes the stages of micronized grinding and then froth flotation applied to the obtained powder tailing material
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