Experimental Study on the Slagging Characteristics of Biomass Briquette Combustion Equipment

Pores in coal and their connectivity are important properties of coal, providing network or channels for gas storage and migration within coal, e.g. during the coalbed methane (CBM) recovery. To investigate the growth characteristics and genetic types of pores in coal in terms of macropore and mesopore, the pores of a high-rank coal were measured by various techniques such as the mercury intrusion method, nitrogen adsorption, focused ion beam scanning electron microscopy (FIB-SEM), and X-ray micro-CT (Computed Tomography). Two high-rank coals formed from regional metamorphism collected from the southern Qinshui basin were selected. The FIB-SEM and X-ray micro-CT provides detailed experimental information for development of a three dimensional (3D) pore network model, which was further used to characterize the pore connectivity. Volume percent of pores of these high-rank coals are dominated by mesopores of approximately 10-50 nm in width, and then followed by micropores, along with the smallest volume percent of macropores. The connectivity within this high-rank coal was mesopore-dominated pore network. Electron microscopy observations further revealed there are coalification-related pores and mineral-related pores in the high-rank coal. The coalification-related pores can be classified as secondary gas pores in organic matter and shrinkage-induced pores around quartz and clay minerals; and the mineral-related pores are developed within minerals, and can be classified as dissolution-created pores and intercrystalline pores. The secondary gas pores are macropores and have poor connectivity. The mineral-related pores can be both macropores and mesopores, and have little influence on pore connectivity due to small content of carbonate minerals in these samples. Under electron microscopy, the shrinkage-induced pores are mainly mesopores. The regional metamorphism, with a high abnormal old thermal field in the research area, is the precondition of the formation of the shrinkage-induced pores. The quartz and clay minerals in the coal provide different formation conditions and hence form different shapes of the shrinkage-induced pores. The coal samples include a large number of shrinkage-induced pores that act as the interconnected pores in the coal and exhibit good connectivity. The quartz and clay minerals play a significant role in developing the interconnected pores in the high-rank coal formed from regional metamorphism.

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Effects of Coal Functional Groups on Adsorption Microheat of Coal Bed Methane

Zhou

Liu

Ye-qing

et al. 2015

Energy Fuels

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This study measured the adsorption heat for five groups of Chinese coal samples of different ranks at 15°C and 0.101 MPa using a C80 microcalorimeter. The functional groups of the coal samples were determined by infrared spectroscopy according to quantum chemical theory. The effects of coalification and coal functional groups on the adsorption heat of coal for methane were discussed in terms of energy. As a result, this study has further perfected the adsorption theory of coal bed methane. The results show that the adsorption heat of coal for methane first increases, then decreases with increasing coal rank and reaches a minimum at the fat coal stage. This indicates that coalification has a significant effect on the characteristics of the adsorption heat of coal for methane. These effects can be clearly classified into stages. Coalification influences the adsorption heat for methane by changing the type of coal, the content of oxygen-containing functional groups, and the pore structure. Oxygencontaining functional groups influence the adsorption heat of coal for methane via the adsorption potential of the methane molecules. In the long-flame coal stage, a high content of oxygen-containing functional groups leads to a high adsorption heat of the coal for methane. In the fat coal to coking stages, large numbers of aliphatic series, aliphatic functional groups, and side chains of aromatic condensed nuclei are removed from the coal molecules under the influence of mechanical compression and dehydration. The decrease in oxygen-containing functional groups results in a decrease in the adsorption potential of the coal and a minimum value of its adsorption heat for methane. In the coking coal stage, the adsorption heat for methane changes little because of the weak influences of mechanical compression and dehydration. In the high-rank coal stage (lean coal and anthracite), the internal surface area of the coal increases, with micropores and transition pores caused by the significantly higher degree of aromatization of the coal. This increase in internal surface area improves the adsorption heat of coal for methane to some extent.

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Experimental Study on the Slagging Characteristics of Biomass Briquette Combustion Equipment

Cited by 4 publications

References 11 publications

Improved fuel conversion through oxygen carrier aided combustion during incineration of biomass-based solid waste in a rotary kiln

Improved fuel conversion through oxygen carrier aided combustion during incineration of biomass-based solid waste in a rotary kiln

FIB-SEM and X-ray CT characterization of interconnected pores in high-rank coal formed from regional metamorphism

Effects of Coal Functional Groups on Adsorption Microheat of Coal Bed Methane

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