Abstract
Low-rank coal is difficult to upgrade using conventional flotation methods due to its high hydrophilic properties. Thus, it is necessary to explore new methods for upgrading and utilizing low-rank coal. In this investigation, a gaseous dodecane pretreatment method was used to enhance the flotation performance of low-rank coal. Pore distribution analysis, FTIR (Fourier Transform Infrared Spectroscopy), and contact angle measurements were used to study the surface properties of the coal sample. Size distribution and float-sink test results indicated that the coal sample contained a lot of clean coal with low ash content, which could be used as a high quality raw material for making coal water slurry. FTIR, pore distribution analysis, and contact angle results showed that the coal was very hydrophilic due to the high concentration of -OH group and the large number of pores and cracks on the coal surface. The hydrophobicity of the coal sample was significantly improved by the gaseous dodecane pretreatment method. Clean coal with 67.2% combustible matter recovery and 10.5% ash content was obtained by gaseous dodecane pretreatment flotation method. Coal water slurry with 60% concentration was prepared using the flotation clean coal.
Highlights
Even though energy research regarding new energy sources and technologies is becoming more popular than those regarding fossil fuels nowadays, coal still accounts for more than 50% of China’s primary energy consumption [1]
A large number of pores and cracks existed on the coal surface, which could be filled by water molecules during the flotation process
The contact angle results indicated that a more stable and hydrophobic coal surface was obtained by gaseous pretreatment (GP) method, which could improve the flotation efficiency of low-rank coal (LRC)
Summary
Even though energy research regarding new energy sources and technologies is becoming more popular than those regarding fossil fuels nowadays, coal still accounts for more than 50% of China’s primary energy consumption [1]. Due to the special nature of China’s resource distribution, a sudden reduction in coal consumption will cause a series of social and economic problems. It is well-known that low-rank coal (LRC) is often used as thermal coal. If the coal slime is directly burned or mixed into other products as medium coal without being upgraded, it will cause waste of resources and environmental pollution. The coal slime usually has a fine particle size, which may be used as a high quality raw material for making coal water slurry (CWS) after being upgraded. The use of LRC slime to make CWS can greatly improve the economic benefits of the enterprise and reduce environmental pollution
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