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Article
Publication date: 12 June 2017

Feng Luo, Guodong Li and Hao Zhang

The purpose of this paper is to obtain the mechanical behavior and damage mechanism of the coal and rock near the stope under the stress state and stress paths of the…

Abstract

Purpose

The purpose of this paper is to obtain the mechanical behavior and damage mechanism of the coal and rock near the stope under the stress state and stress paths of the surrounding rock with the dynamic mining.

Design/methodology/approach

Through the three-axial compression test and the uniaxial compression test by meso experiment device, the mechanical behavior and fracture evolution process of coal and rock were studied, and the acoustic emission (AE) characteristics under uniaxial compression of the coal and rock were contrasted.

Findings

Under the three-axial compression, the strength of coal and rock enhance significantly by confining pressure. The volume of outburst coal shows obvious stages: compression is followed by expansion. The coal first appear to undergo compaction under vertical stress due to volume decrease, but with the development of micro- and macro-cracks, the specimens appeared to expand; under the uniaxial compression, through the comparison of stress–strain relationship and the crack propagation process, stress drop and fracture of coal have obvious correlation. The destruction of coal was gradual due to the slow and steady accumulation of internal damage. Due to the influence of the end effect, the specimens show the “conjugate double shear failure”. The failure process of the coal and rock and the characteristics of the AEs have a corresponding relationship: the failure causes a large number of AE events. Before the events peak, there was an initial stage, calm growth stage and explosive growth stage. There were some differences between the rock and coal in the characteristics of the AE.

Originality/value

These research studies are conducted to provide guidance on the basis of mine disaster prevention and control.

Details

World Journal of Engineering, vol. 14 no. 3
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 21 August 2013

Yingbin Guan, Chanyu Guo and Haimei Li

The coal-bearing strata of Longdong mine field in Xingtai is the Carboniferous-Permian. The No.8 coal seam is located in the Taiyuan formation and is the main minable coal

Abstract

The coal-bearing strata of Longdong mine field in Xingtai is the Carboniferous-Permian. The No.8 coal seam is located in the Taiyuan formation and is the main minable coal-bed. The coal is mainly gas-fat coal accompanied with coking coal, lean coal and anthracite. The results of the macroanalysis and maceral quantitative analysis on the main minable coal-bed show that the degree of coal metamorphism takes the old town as the center and is distributed concentrically outward and the anthracite and lean coal are distributed nearby the old town, and the coal gradually becomes coking coal, gas-fat coal and gas coal further outwards. The degree of coal metamorphism was affected by regional metamorphism, and the coal seams which are close to the old town stack the regional magmatic thermal metamorphism. The conclusions of the research offer a scientific foundation to exploit the coal resource in this area?

Details

World Journal of Engineering, vol. 10 no. 4
Type: Research Article
ISSN: 1708-5284

Keywords

Expert briefing
Publication date: 20 April 2016

Trends in China's coal use.

Details

DOI: 10.1108/OXAN-DB210646

ISSN: 2633-304X

Keywords

Geographic
Topical
Article
Publication date: 24 July 2019

Agnieszka Kijo-Kleczkowska

The paper aims to undertake coal–water suspension combustion, in air and in fluidised bed conditions. Fluidised bed conditions are the best to efficiently and ecologically…

Abstract

Purpose

The paper aims to undertake coal–water suspension combustion, in air and in fluidised bed conditions. Fluidised bed conditions are the best to efficiently and ecologically use fuel. Combustion technologies using coal–water fuels create a number of new possibilities for organising combustion processes so that they fulfil contemporary requirements. The aim of the process was to show how the specificity of combustion of coal–water suspensions in the fluidised bed changes the kinetics of the process, compared to combustion in the air stream. Changes of the surface and the centre temperature and mass of the coal suspension during combustion, and evolution of fuels during process are presented in the paper.

Design/methodology/approach

Experimental character of the research required the research stand preparation, as well as working out of the measurements methodology (Kijo-Kleczkowska, 2010). The research stand (Figure 1a) was made of ceramic blocks in which the quartz pipes were put. The heating element of the stand comprised three heating coils of 2.0 kW. Each heater was placed in small quartz tubes. These tubes were built into the quartz tube which was thermally insulated by fibre material Al2O3 and which was covered with steel sheet. Combustion chamber constituted the quartz pipe, which was additionally insulated thermally, to keep the necessary temperature of the entering gas and to reduce the heat loss. The compressed air was transported to the quartz tube through the electro-valve, the control valve and the rotameter. This study stand allowed for the comparison of the combustion process of coal–water suspensions, in air and in fluidised bed conditions. To study in the fluidised bed, quartz sand was used. Depending on the velocity of air inflowing from the bottom of the bed, different bed characteristics were obtained – from bubble – to circulating-beds. The fumes were removed outside by means of a fan fume cupboard. To regulate the temperature inside the combustion chamber, the Lumel microprocessor thermoregulator was applied. The regulator controlled the work of tri-phase Lumel power controller supplying the main heating elements (gas heater) allowing to measure the actual temperature with accuracy of measurements to 20°C. The temperature measurements in the combustion chamber were carried out by means of the thermocouple NiCr-NiAl. To establish the centre and surface temperature and mass of the fuel, a special instrument stalk was constructed (Figure 1b). It had two thermocouples PtRh10-Pt, placed in two thin quartz tubes connected to the scale. One of the thermocouples was located inside the fuel, while the other served as a basket which was to support the fuel. It also touched the surface of the fuel. The thermocouples were connected to the computer to record the experimental results. The essential stage of the preliminary work was to make out a suspension, which was a mixture of fuel dust (hard coal dust or dried coal-sludge dust) and water. To produce the suspension it was necessary to prepare fuel dust after grinding and sifting it, and then adding water, to obtain a suspension moisture of 20, 35 or 50 per cent. The hard coal was applied in the research. The analysis of fuel dust (in air-dry state) is shown in Table I. The testing of the porosity of fuel was made with mercury porosimetry, carried out in the Pascal 440 apparatus, applying pressure from 0.1 to 200 MPa. This method involves the injection of mercury into the pores of the fuel, using high pressures (Kijo-Kleczkowska, 2010).

Findings

1. Under experimental conditions, during combustion in the fluidised bed, intensive heating of the suspension is observed in the initial stage of the process, followed by the removal of heat from the suspension by the contacting quartz material, leading to lowering of the average fuel temperature and extension of the combustion time, compared to the process carried out in air. 2. Measurements using mercury porosimetry enable the identification of the change of suspension porosity. 3. Devolatilisation and combustion of volatiles lead to an increase in the pores’ size in the fuel and their coalescence. 4. Combustion of fuel leads to the development of cracks in the suspension, and its structure changes under the influence of temperature. Cracks are caused by the formation of thermal stresses inside the fuel. 5. Under experimental conditions, suspension combustion in the fluidised bed causes an increase in volume participation of pores, with larger sizes of pores (3,500-5,000 nm), compared to combustion in the air.

Originality/value

The paper undertakes the evolution of suspension fuel, made of a hard coal and a coal-sludge, during combustion in air and in the fluidised bed.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Expert briefing
Publication date: 7 December 2017

His remarks follow an Indonesian Coal Mining Association forecast in November that coal consumption in 2017 had increased 16% over 2016's levels. The rise in domestic coal

Article
Publication date: 1 October 1979

Robert M. Davidson

The subject coverage of the Coal Data Base is very large and represents an amalgam of the interests of the member countries who supply input. The basic coverage is as…

Abstract

The subject coverage of the Coal Data Base is very large and represents an amalgam of the interests of the member countries who supply input. The basic coverage is as listed in the contents page of Coal Abstracts:

Details

Aslib Proceedings, vol. 31 no. 10
Type: Research Article
ISSN: 0001-253X

Article
Publication date: 1 September 1969

John Thompson

Coal‐tar pitch, either in its simple form or as part of more complicated formulations, is being increasingly used in modern times for the heavy‐duty protection of…

Abstract

Coal‐tar pitch, either in its simple form or as part of more complicated formulations, is being increasingly used in modern times for the heavy‐duty protection of steelwork, concrete, non‐ferrous metals, etc. wherever the utmost in resistance to corrosion is required. Wailes Dove Bitumastic Ltd., of Hebburn, Co. Durham, have been specialists in coal‐tar pitch compositions for over 100 years and are in the vanguard of research to extend its possibilities to keep pace with modern needs for corrosion prevention. This report traces the development of coal‐tar pitch from its use as a simple, single material to its use in the most modern and advanced type of coatings.

Details

Anti-Corrosion Methods and Materials, vol. 16 no. 9
Type: Research Article
ISSN: 0003-5599

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