Effect Of Volatile-char Interaction On Volatilization Of Sodium And Char Structure During Zhundong Coal Pyrolysis

Now Zhun Dong region of Xinjiang found is of rich reserves of coal resources, the current petroleum reserves has been more than 2000 hundred million tons. Zhun Dong coalfield is to be a safeguard of continuing to supply an important source of coal energy to our country. On the one hand, sodium is a kind of good catalyst in the process of pyrolysis and gasification; on the other hand, the high amount of sodium will lead to the rear of the boiler slagging and defiled, leading to a sharp drop in heat utilization efficiency. And volatile-char interaction affect almost every aspect in the process of heat utilization. The effects of interaction between volatile-char is studied on sodium release and char structure, could have a comprehensive understanding of Zhun Dong coal pyrolysis gasification mechanism, and to ensure clean utilization of Zhun Dong coal is of great significance.In this paper, the experimental sample includes Zhun Dong raw coal and acid-pickling coal. In addition, using graphene-Na as loading carboxylic acid sodium char model compounds for the volatile-char interaction experiment research. Pyrolysis experiment is operated in the two-stage fluidized bed/fixed bed reactor system. And by using microwave digestion instrument, inductively coupled plasma atomic emission spectrometer(ICP-AES) and micro Raman spectrometer test apparatus, the experiment that the sodium content in char and char structure is analyzed.Research on volatile-char interaction’s effect in the process of Zhun Dong pyrolysis on sodium content of raw coal sample and char structure. At low temperature under 500℃ and 700℃, volatile-char interaction will block the release of sodium. And under the high temperature of 900℃, volatile-char interaction can significantly increases the release of sodium. Volatile of hydrogen at 900℃ was not involved in process of the release of sodium in char. The main cause of volatile-char interaction forcing Na release may be that free radicals in the volatile caused significant release of sodium. Under 500℃ and 700℃, the effects of temperature on amorphous carbon into microcrystalline process is not significant.But when there is interaction between volatile and char, the degree of order of char is increased, but amorphous carbon is reduced, and at a higher temperature the interaction process to promote the process of microcrystalline generation is also more obvious. Volatile-char interaction at 500℃ can promote aromatic ring fracture process of char, and with the increase of temperature, this promote affect is weakening. Until 900 ℃ the interaction almost does not affect the fracture process of aromatic ring.Research on volatile-char interaction’s effect in the process of pyrolysis of graphene-Na on sodium content release and char structure. Volatile-char interaction on graphene-Na and char graphitizing process effect is different. The reason may be due to the carboxylic acid sodium inside the graphene, the radicalin volatile is in substitution reaction in char, replace the Na to release, and the original acid sodium position changes into other forms of acid or other hydroxy acid, then it continues to decompose with the increase of temperature,to release CO2 and other gases. The process is blocking the increase of crystallite structure size in graphene-Na, not conducive to the process of microcrystalline form, therefore delaying the process of graphitization, so the change trend of char is not the same as the graphene-Na.