Abstract
The purpose of this study is to investigate the catalytic effects of alkali and alkaline earth metallic species (AAEM) on char conversion during the gasification in steam and the changes in ex-situ char reactivity in oxygen after the gasification in steam using different forms (i.e. H-form, Na-form) of Shengli brown coal. The surface area, AAEM concentration and carbon crystallite of chars were obtained to understand the change in char reactivity. It was found that not only Na concentration and carbon structure were the main factors governing the char reactivity in the atmosphere of steam and oxygen, but also they interacted each other. The presence of Na could facilitate the formation of disordering carbon structure in char, and the amorphous carbon structure would in turn affect the distribution of Na and thus its catalytic performance. The surface area and pore volume had very little relationship with the char’s reactivity. Additionally, the morphology of chars from different forms of coals were observed using scanning electron microscope (SEM).
Highlights
Coal is the main energy source in China
The purpose of this study is to investigate the catalytic effects of alkali and alkaline earth metallic species (AAEM) on char conversion during the gasification in steam and the changes in ex-situ char reactivity in oxygen after the gasification in steam using different forms (i.e. H-form, Na-form) of Shengli brown coal
3 Results and discussion char yields from 0.02H-form coal than 5H-form coal before 800 °C (Kashimura et al 2004). It appears that the effects of additional loss of AAEM and humic acid material on the char yields were ignorable when the gasification temperatures were higher than 800 °C
Summary
Coal is the main energy source in China. The continuous improvement of living standards will continue to lead to drastic increases in the demand for energy. Coal gasification is the key and main technology of clean coal transformation and utilization technology (production of chemicals, hydrogen and liquid fuels etc.) (Bretz 1992; Gary and Russell 2001; Hayashi et al 2002; McKendry 2002; Li 2004, 2007). The fast heating rate inevitably caused high volatilizations of AAEM, which would be partially present in the product gases cleaning process could remove most of them. The advantages of brown coal gasification at slow heating rates would be obtaining cleaner syngas with less tarry material and AAEM the reaction rate and char conversion were expected to be slower than that of fast heating rate. The multiple ending products from slow heating gasification of brown coal may have a bright future
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