Search

Dry deshaling is receiving renewed attention in the coal-mining industry. In this methodology, high-density rock is removed from run-of-mine (ROM) coal at the mine extraction point and prior to shipping. One of the popular technologies used globally, the density-based vibrating air-table, was tested on a pilot-scale at three different coal-processing facilities in India. In this article, statistical analysis of the resulting test data was conducted using response surface methodology (RSM). The study identified that out of the four major operating parameters (i.e., tilt, slope, fan speed, and table vibrations), vibration frequency and its combined effect with slope impact the deshaling performance the most. In addition, empirical equations formulated using regression analyses were used for simultaneous optimization of the significant parameters in order to achieve the highest performance for the separation of Indian coals. The optimal operating conditions were determined using a desirability functi...

Coal mining and processing operations have in the past and continue to create large tonnages of fine coal and waste particles. While technological advances in wet processing has made it possible to efficiently recover coal fines, difficulties associated with dewatering make these fine particles unattractive economically for most coal markets. A novel system has been developed for cleaning fine raw coal utilizing a multistage dry classification process that removes the clay particles that are typically much smaller than the majority of the clean coal particles and that reduces the product surface moisture to as low as 1%. In this article, the novel dry coal-cleaning process under license to Greenfields Coal Company was evaluated. The classification process offers a viable alternative to traditional wet processing and dewatering of the fine particles, especially for operations recovering abandoned impoundments where a sufficient water source and/or a waste slurry disposal site are unavailable. This article ...

The potential of dry cleaning coal of varying ranks using a pneumatic table concentrator has been evaluated as part of an ongoing investigation. The evaluation has been performed at several sites throughout the United States where coal is extracted from surface open cast, highwall and underground operations as well as from coarse reject. The treated coals varied in feed ash content (i.e., 7–70%). Regardless of the mineral matter type, pure rock removal into the reject stream was achieved in all applications with little coal loss. Field data obtained when treating 50 × 6 mm run-of-mine bituminous coal indicate that 70–90% of the >2.0 Relative Density (RD) rock can be rejected. As a result, a clean product having acceptable market quality was generated from several coal sources including lignite, sub-bituminous, and bituminous coals. This article provides an overview of data from recent field testing of the dry air table technology and discusses the potential implementation strategy for the various sites ev...

This report documents the status of flexural strength evaluations from current ASTM procedures and of developing finite element models predicting the probability of failure. This work is covered under QLD REC-00030. Flexural testing procedures of the American Society for Testing and Materials (ASTM) assume a linear elastic material that has the same moduli for tension and compression. Contrary to this assumption, graphite is known to have different moduli for tension and compression. A finite element model was developed and demonstrated that accounts for the difference in moduli tension and compression. Brittle materials such as graphite exhibit significant scatter in tensile strength, so probabilistic design approaches must be used when designing components fabricated from brittle materials. ASTM procedures predicting probability of failure in ceramics were compared to methods from the current version of the ASME graphite core components rules predicting probability of failure. Using the ASTM procedures yields failure curves at lower applied forces than the ASME rules. A journal paper was published in the Journal of Nuclear Engineering and Design exploring the statistical models of fracture in graphite.

This report outlines the development of finite element models used to determine temperature and stresses in a prismatic core reflector block. This initial analysis determines an appropriate temperature distribution in a prismatic reflector from limiting conditions in the adjacent fuel block based on simplifying assumptions.

The available grades of graphite for the NGNP are reviewed. A selection matrix is presented outlining the available grades for the NGNP graphite irradiation program based upon input from potential NGNP vendors, graphite manufactures, and graphite experts.

Twenty-eight healthy trained and untrained men and eleven untrained women were exercised at several grades on a treadmill or in various athletic events. The serum levels of five enzymes (two transaminases, aldolase, and two dehydrogenases) were compared prior to and at intervals after work. Generally there was a rise after exercise which reached its peak 5 min after completion of the work. The greatest increment of enzyme increase was observed in the untrained subjects and the least in the trained athletes. As the total amount of work output increased the mean serum enzyme levels were correspondingly raised. Aldolase and lactic dehydrogenase showed the least change, malic dehydrogenase increased moderately, while the two transaminases manifested very significant rises after all forms of exercise. Submitted on September 5, 1961