2004아테네 올림픽대회출전 한국레슬링 대표선수의 무산소성 운동능력 및 등속성 근력

Classification Methods For Remotely Sensed Data

Effects of air volume ratio parameters on air curtain dust suppression in a rock tunnel’s fully-mechanized working face

Coal oxidation at low temperatures is the heat source liable for the self-heating and spontaneous combustion of coal. This phenomenon has imposed severe problems in coal related industries. Attempts to understand this phenomenon by previous researchers have provided significant progress. It is well-known that coal oxidation at low temperatures involves oxygen consumption and formation of gaseous and solid oxidation products. This process is majorly influenced by temperature, oxidation history of coal, coal properties, particle size distribution of the coal, etc. The current understanding of the phenomenon of self-heating and spontaneous combustion of coal is discussed along with the different experimental and numerical models established to predict self-heating characteristics of coal. This paper focuses on the global position of the study carried out by academics, research institutes and industries on spontaneous combustion of coal and coal mine fires. Within this framework, the generally used spontaneous combustion techniques to predict the spontaneous combustion liability of coal were evaluated. These techniques are well-known in their usage, but no specific method has become a standard to predict the spontaneous combustion liability. Further study is still needed to indicate a number of impending issues and to obtain a more complete understanding on the phenomenon.

A review of research on spontaneous combustion of coal

Some developments and new insights of environmental problems and deep mining strategy for cleaner production in mines

Spontaneous combustion of coal is a well-known phenomena around the globe. Apart from the coal itself, burning coal-shales is becoming a problem in the South African coal mines. Serious incidents of spontaneous combustion have been reported as a result of self-heating of reactive coal-shales. The intrinsic properties and spontaneous combustion tests of 28 selected coal and coal-shale samples were conducted and a relationship between the two has been established. Intrinsic properties were obtained by using the proximate and ultimate analysis, and spontaneous combustion liability tests results were obtained by using the Wits-Ehac and Wits-CT indices. The experimental results show that intrinsic properties of these materials complement to the spontaneous combustion liability tests results. Comparative analyses of intrinsic properties and spontaneous combustion characteristics indicate similarities between the mechanism of coal oxidation and that of the oxidative processes undergone by coal-shales. For the tested samples, coal samples have a higher intrinsic spontaneous combustion reactivity rating than the coal-shales. Furthermore, an increase in carbon, moisture, hydrogen, volatile matter, nitrogen and a decrease in ash content indicate an increased proneness to self-heating. The concentration of pyrite found in the coal-shales accelerates self-heating. The event of spontaneous combustion can occur if coal-shales absorb sufficient oxygen when subjected to atmospheric conditions.

Spontaneous combustion of coals and coal-shales

The spontaneous combustion liability of coal can be determined by using different experimental techniques. These techniques are well-known in their application, but no certain test method has become a standard to prove the reliability of all of them. A general characterisation which included proximate and ultimate analyses, petrographic properties and spontaneous combustion tests (thermogravimetric analysis (TGA) and the Wits-Ehac tests) were conducted on fourteen coal and four coal-shale samples. The spontaneous combustion liability of these samples collected between coal seams (above and below) were predicted using the TGA and the Wits-Ehac tests. Six different heating rates (3, 6, 9, 15, 20 and 25 °C/min) were selected based on the deviation coefficient to obtain different derivative slopes and a liability index termed the TGspc index. This study found that coal and coal-shale undergo spontaneous combustion between coal seams when exposed to oxygen in the air. Their intrinsic properties and proneness towards spontaneous combustion differ considerably from one seam to the other. The Wits-Ehac test results agreed with the TGspc results to a certain extent and revealed the incidents of spontaneous combustion in the coal mines.

Spontaneous combustion liability between coal seams: A thermogravimetric study

This study presents a review of the various methods to predict the spontaneous combustion liability of coal and coal-shale. The relative propensity of coal to undergo self-heating can be established by different methods. These methods are well established in their usage, but the fact that no particular test method has become a standard to predict the spontaneous combustion liability indicates that doubt still exists as to the validity of all of them. The underlying principle of all the tests is that the more readily the coal undergoes exothermic oxidation, the more liable it is to self-heat. Comprehensive studies that centres on the international position on research being conducted by academics, different research institutes and industries on spontaneous combustion of coal and coal mine fires were evaluated. Relationships between the geochemical analysis (proximate and ultimate analysis, forms of sulphur, petrographic properties, X-ray diffraction and X-ray fluorescence) and spontaneous combustion testing methods (numerical and experimental approaches) used to predict the spontaneous combustion liability of coal were reviewed. The combination of these tests provides a better understanding of the mechanism that controls the spontaneous combustion phenomena. However, irrespective of the extensive studies that have been conducted over time, spontaneous combustion is still a major problem in the coal value chain.

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B. Genc

Papers

A review of research on spontaneous combustion of coal

Spontaneous combustion of coals and coal-shales

Spontaneous combustion liability between coal seams: A thermogravimetric study

Spontaneous combustion liability of coal and coal-shale: a review of prediction methods

Influence of antioxidants on spontaneous combustion and coal properties