Mineral Processing
I. Kursun Unver; M. Terzi
Abstract
Today coal is among the most important energy sources. In order to meet the world's energy demands, low-calorie lignite with a high ash content is generally used in the large capacity coal-fired thermal power plants. As a result of coal firing, wastes such as fly ash, slag, and flue gas are also produced. ...
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Today coal is among the most important energy sources. In order to meet the world's energy demands, low-calorie lignite with a high ash content is generally used in the large capacity coal-fired thermal power plants. As a result of coal firing, wastes such as fly ash, slag, and flue gas are also produced. Subsequently, toxic trace elements within coal are transferred to wastes such as slag, fly ash, and flue gases. Large amounts of these, which are usually stored in collection ponds or stockpiles, are problematic in terms of environment. Although coal fly ash (CFA) has been utilized in construction and several other industries for decades, its current ratio of utilization is still quite limited. As an important fact, CFA also contains many valuable metals including germanium (Ge), gallium (Ga), vanadium (V), titanium (Ti), and aluminum (Al). In addtion, coal and CFA can be regarded as alternative sources of radioactive elements. Therefore, they also have a great potential in terms of the precious metals and trace elements they contain. In this study, the present literature on the distribution of trace elements in coal and coal ash during firing and ore preparation processes and their recovery possibilities with mineral processing practices are reviewed. While many research works on the subject clearly indicate that the large amounts of the ashes produced from firing of coal could be problematic in terms of environment, many studies and practices also show that coal combustion products also have a great potential in terms of the precious metals and trace elements.
Exploitation
S. Moosazadeh; H. Aghababaie; Seyed H. Hoseinie; B. Ghodrati
Abstract
Utilization is one of the main managerial factors that is applied for construction process analysis well. It directly affects the project duration and construction costs. Therefore, a utilization study in tunneling projects is essential. In this work, the utilization of an earth pressure balance Tunnel ...
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Utilization is one of the main managerial factors that is applied for construction process analysis well. It directly affects the project duration and construction costs. Therefore, a utilization study in tunneling projects is essential. In this work, the utilization of an earth pressure balance Tunnel Boring Machine (TBM) in Tabriz urban railway project was studied using the Monte Carlo simulation approach. For this purpose, the unit operation during one working shift such as boring time, ring building time, and locomotive travel time was recorded and saved in data base. In addition, the general down times such as TBM and back-up system maintenance, surface and tunnel logistic maintenance, cutting tools’ replacement, and locomotive delay times were recorded and considered in simulation. The results of this work show that the mean simulated project duration time of case study TBM is approximately 859 shifts and close to the real data with a difference of 0.92%. Finally, the average estimated utilization factor was found to be approximately 14%.
Omid Frough; Seyed Rahman Torabi; Majid Tajik
Abstract
Successful application of a TBM in a project requires investigating both the ground conditions and the machine and backup system design features. Prediction of the machine performance is very important as it has a big effect on the duration of the project and the costs. In this respect, both penetration ...
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Successful application of a TBM in a project requires investigating both the ground conditions and the machine and backup system design features. Prediction of the machine performance is very important as it has a big effect on the duration of the project and the costs. In this respect, both penetration rate and advance rate must be estimated. Utilization factor, which depends on the type of operation, management, maintenance, geological conditions, mucking delays and other downtimes, correlates the advance rate and penetration rate. Adverse rock mass conditions such as mixed face condition, water problem and instability of rock have a great role in TBM downtimes and reduce the machine utilization considerably. Based on detailed engineering geological reports and maps and daily site reports taken from Karaj-Tehran Water Conveyance Tunnel ( Lots 1 and 2), this paper evaluates, main rock mass properties utilized for the estimation of TBM performance and discusses their effect on the machine utilization. . More specifically it uses the developed database also contains daily boring time, different rock mass related downtimes, daily advance and length of bored tunnel in each engineering geological units. It is concluded that the percentage of the rock mass related downtimes can be estimated via RMR within reliable coefficient of determination.
