A review on water in low rank coals: The existence, interaction with coal structure and effects on coal utilization

Some recent advances in the understanding of the pyrolysis and gasification behaviour of Victorian brown coal

Formation of the structure of chars during devolatilization of pulverized coal and its thermoproperties: A review

Coal combustion for power generation is a major source of particulate air pollution. Understanding of the formation mechanisms and properties of coal combustion aerosols is critical to both the development of particulate control technologies and the assessment of their impacts on human health. This paper presents an overview of the current understanding of the mechanisms of ash particle formation in major coal-based power generation processes such as pulverized coal combustion, fluidized bed combustion and coal gasification, and a summary of the aerosol properties that are important for elucidating particle formation and evaluating their health effects. Principal particle formation mechanisms, including mineral coalescence, particle fragmentation, and vaporization-condensation, are reviewed. The complex nature of the formation mechanisms of submicron aerosols is emphasized. Evidence is provided for some solid-to-particle processes that are suspected to contribute to the formation of the submicron aerosols. Physicochemical properties such as particle size, composition and morphology are discussed. Of particular interest is the trimodality of the ash aerosol size distribution. Size-resolved elemental composition data are used to identify particle modes and to uncover their formation mechanisms. The formation of the additional central particle mode is attributed to heterogeneous condensation of vaporized species on existing fine residual ash particles. Future research topics associated with ash aerosol formation and properties are discussed.

Coal combustion-generated aerosols: Formation and properties

Volatilisation and catalytic effects of alkali and alkaline earth metallic species during the pyrolysis and gasification of Victorian brown coal. Part VII. Raman spectroscopic study on the changes in char structure during the catalytic gasification in air

Char samples prepared in a pressurized entrained flow reactor (PEFR) at a pressure of 2.0 MPa and in a drop tube furnace (DTF) at atmospheric pressure have been examined. Chars generated in the PEF...

Effect of Pressure on Char Formation during Pyrolysis of Pulverized Coal

Dewatering/drying of Victorian brown coal will be an integral part of future brown coal utilization processes aimed at the reduction of greenhouse gas emissions. This study aims to investigate the effects of the thermal pretreatment of brown coal in the presence of steam/water on its subsequent pyrolysis behavior. A Victorian (Loy Yang) brown coal was thermally pretreated in pressurized steam and inert atmospheres. The pyrolysis behavior of these pretreated coal samples was investigated in a wire-mesh reactor. While the pretreatment in steam at temperatures higher than 250 °C increased the char yield of the steam-treated coal, it did not affect the overall pyrolysis char yield at 1000 °C s-1 if the weight loss during the pretreatment in steam was also considered. However, the tar yield decreased significantly after the pretreatment in the presence of steam. The UV-fluorescence spectroscopy of tars revealed that the release of large aromatic systems from the steam-treated coal was only affected by the pret...

Effects of pretreatment in steam on the pyrolysis behavior of loy yang brown coal

This study aims to investigate the effects of dewatering on the primary pyrolysis behavior and gasification reactivity of Victorian brown coal. Dewatered brown coal samples were prepared by dewatering/drying of the brown coal in steam and by means of mechanical thermal expression (MTE). The primary pyrolysis behavior and gasification reactivity of these dewatered coal/char samples were evaluated in a wire-mesh reactor and in a thermogravimetric analyzer (TGA), respectively. It was found that changes in the physical structure of the brown coal and the loss of NaCl during dewatering at low temperatures did not significantly affect the char and tar yields. However, dewatering/drying at temperatures > 250 °C not only reduced the volatile yield but also shifted the normalized derivative thermogravimetric (DTG) peak to a higher temperature during pyrolysis in the TGA under constant heating rates. The analysis of the pyrolysis kinetics of dewatered brown coal samples using a distributed activation energy model i...

Effects of Dewatering on the Pyrolysis and Gasification Reactivity of Victorian Brown Coal

Accurate prediction of the severity of ash deposition on heat transfer surfaces in pulverised fuel fired furnaces has been the driving force of many studies. These studies initially attempted to develop engineering indices, which could be used to predict the severity of deposition from a particular coal, based on bulk analysis of the coal prior to utilisation [Raask, 1985]. The indices developed were only applicable to certain coal ash chemistries and found little application for other coals. A number of studies were then undertaken to determine the behaviour of specific minerals [Srinivasachar, 1990a, 1990b], which allowed interpretation of experimental and industrial scale data in terms of mineral specific reactions. Iron in coal has long been linked with slagging. Consequently, several engineering indices make some allowance for iron content when predicting deposition severity [Juniper, 1995]. The Northern Hemisphere coals upon which these indices are based generally contained pyrite as the principal form of iron. In Australian coals iron is predominantly in the form of carbonates, hence the engineering indices developed for the Northern Hemisphere coals would only loosely apply to Australian coals. Siderite limestone dolomite where MgO 4055wt.%) and ankerite are the principal carbonate minerals found in Australian coals. The variable compositions found for siderite in Australian coals led Patterson et al. 1994 to classify four main types. Siderite (where is the

Hongwei Wu

Papers

Effect of Pressure on Char Formation during Pyrolysis of Pulverized Coal

Effects of pretreatment in steam on the pyrolysis behavior of loy yang brown coal

Effects of Dewatering on the Pyrolysis and Gasification Reactivity of Victorian Brown Coal

IRON IN COAL AND SLAGGING The Significance of the High Temperature Behaviour of Siderite Grains During Combustion

Effects of volatile-char interactions on the reactivity of chars from the pyrolysis of brown coals